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Abstract Background A long-term follow-up of close contacts to monitor their infection status is essential to formulate a promising screening strategy. The study aimed to assess the dynamics of tuberculosis (TB) infection using Interferon-γ release assay (IGRA) and determine risk factors associated with TB infection. Methods Definite TB patients were interviewed and their household contacts were screened for TB infection by IGRA during 12-month longitudinal investigation. Results We included in our analyses 184 household contacts of 92 index TB patients. 87 individuals (47.3%) in contact group progressed to TB infection, of whom 86 developed into IGRA positive within 24 weeks. Close contacts with a higher age and comorbidities are easier to exhibit TB infection. Analysis showed that risk factors for becoming IGRA-positive individuals included residence, older age, comorbidities, BCG scar and high bacterial load. Contacts with BCG scar had a lower IGRA-positive rate. Conclusion IGRA conversion generally occurs within 24 weeks after exposure. The TB transmission happens since subclinical TB stage and the presence of BCG scar is an independent protective factor reducing risk of TB infection among close contacts. Repeated IGRA tests are sensible to conducted among close contacts at 24 weeks after exposure to identify the IGRA-positive individuals.

Background: A long-term follow-up of close contacts to monitor their infection status is essential to formulate a promising screening strategy. The study aimed to assess the dynamics of tuberculosis (TB) infection using Interferon-γ release assay (IGRA) and determine risk factors associated with TB infection. Methods: Definite TB patients were interviewed and their household contacts were screened for TB infection by IGRA during 12-month longitudinal investigation. Results: We included in our analyses 184 household contacts of 92 index TB patients. 87 individuals (47.3%) in contact group progressed to TB infection, of whom 86 developed into IGRA positive within 24 weeks. Close contacts with a higher age and comorbidities are easier to exhibit TB infection. Analysis showed that risk factors for becoming IGRA-positive individuals included residence, older age, comorbidities, BCG scar and high bacterial load. Contacts with BCG scar had a lower IGRA-positive rate. Conclusion: IGRA conversion generally occurs within 24 weeks after exposure. The TB transmission happens since subclinical TB stage and the presence of BCG scar is an independent protective factor reducing risk of TB infection among close contacts. Repeated IGRA tests are sensible to conducted among close contacts at 24 weeks after exposure to identify the IGRA-positive individuals. [ABSTRACT FROM AUTHOR]

ObjectivesBefore vaccines and effective treatments were available, quarantine of close contacts was important to limit the spread of SARS-CoV-2. To evaluate potential benefits and harms of quarantine, we aimed to estimate infection rates and describe experiences and mental health among persons in mandated quarantine during the early SARS-CoV-2 pandemic.MethodsWe invited adults in mandated quarantine after an exposure to SARS-CoV-2 identified through contact tracing of the Canton of Zurich, Switzerland, between August 2020 and January 2021. Participants completed two questionnaires and received up to two SARS-CoV-2 polymerase chain reaction tests, during and at the end of quarantine.ResultsAmong 395 participants, quarantine duration ranged from 2 to 20 days. By day 11 since the last contact, 11.1% [95% CI 8.4%–14.7%] were infected with SARS-CoV-2. The proportion of participants with symptoms of depression doubled from 9.3% before quarantine to 18.9% during quarantine, and 12.1% reported quarantine was very or extremely difficult.ConclusionAlthough quarantine was only moderately burdensome for most participants, some experienced significant difficulties and burden. Policymakers need to balance infection control with potential harms placed on individuals.

Background and aims: COVID-19 has emerged as a novel pandemic, emphasizing the crucial role of prevention and quarantine measures. Compliance with these measures becomes particularly important for individuals in close contact with COVID-19-infected individuals. This study aimed to investigate the level of quarantine compliance among individuals who had close contact with COVID-19 patients in Hamadan province, as well as identify predictors associated with compliance. Methods: This descriptive-analytical, cross-sectional study was conducted between March and July 2022, involving 350 individuals who had close contact with COVID-19 patients in Hamadan province, Iran. A researcher-designed questionnaire was employed to gather participants’ demographic and clinical information, as well as their adherence to quarantine principles, through a 7-question assessment. The collected data were statistically analyzed using Stata software, version 16. Results: The study participants had a mean age of 40.23±12.91 years. The rate of good compliance with quarantine measures among individuals in close contact with COVID-19 patients was found was 58.66%. Adjusted logistic regression analysis revealed that men in close contact with COVID-19 patients had a 1.66 times higher chance of complying with quarantine compared to women (odds ratio [OR]=1.66, 95% CI=1.06, 2.56), P=0.025). Additionally, individuals over the age of 60 who had close contact with COVID-19 patients exhibited a 2.28 times higher chance of non-compliance with quarantine (OR=2.28, 95% CI=1.17, 4.45, P=0.015). Conclusion: Demographic characteristics could significantly influence compliance with quarantine principles among individuals in close contact with COVID-19 patients. Addressing these factors is crucial for effective health planning and patient education in the country.

ObjectiveTo investigate the latent tuberculosis infection （LTBI） of close contacts in schools of Xuhui District， and to explore the tuberculin skin test （TST）- interferon-γ release assay （IGRA） two-step method in order to discover the screening strategy of tuberculosis in Xuhui District.MethodsClose contacts of tuberculosis in schools of Xuhui District from 2020 to 2022 were selected as research subjects. Screening was conducted using symptom questionnaire， TST， chest X-rays， IGRA， and the information including the etiological results and grade of the index cases， as well as gender， age， and relationship with the index cases of the research subjects were collected.ResultsTotally 615 close contacts of 32 tuberculosis cases occurred in the schools were finally included. Of the 609 close contacts who completed tuberculosis infection screening and underwent TST testing， 153 TST（+） individuals underwent IGRA testing. The final LTBI rate was 4.6%， and the pulmonary tuberculosis detection rate was 163 per 100 000. The relationship with the index cases was an influencing factor for LTBI. The IGRA positivity rate was higher among close contacts with TST ≥15 mm than among those with 10 mm≤ TST

From 6 Jan 22 to 17 Feb 22, a total of 729,367 close contacts classified into four distinct groups (i.e., household, social, school and nursing/ welfare home contacts) were managed by the Health Risk Warning system. High COVID-19-positive rates were demonstrated amongst household contacts, i.e., 10.9% (37,220/342,302) were detected via antigen rapid test kits and 56.5% (4,952/8,767) were detected via polymerase chain reaction testing. Household contacts represent the highest risk of being infected by virtue of the sustained close-proximity interactions in the household setting. Social, school and nursing/ welfare home contacts continue to remain at-risk groups for close monitoring. At a population level, household and symptomatic close contacts should be the groups of focus in the early phases of the pandemic, including future potential waves involving COVID-19 variants of concern. [ABSTRACT FROM AUTHOR]

Abstract Background Individuals in close contact with active pulmonary tuberculosis (TB) patients showed a high risk of recent infection and, once infected, higher risk of developing active TB in the following years post-exposure. But the peak time of active disease onset is unclear. This study aims to estimate post exposure TB incidence risk among close contacts to provide reference for clinical and public health strategies. Methods We searched PubMed, Web of Science, and EMBASE for articles published until December 1, 2022. The incidence rates were quantitatively summarized by means of meta-analysis using the random-effect model. Results Of the 5616 studies, 31 studies included in our analysis. For baseline close contacts results, the summarized prevalence of Mycobacterium tuberculosis (MTB) infection and active TB was found to be 46.30% (95% CI: 37.18%-55.41%) and 2.68% (95% CI: 2.02%-3.35%), respectively. During the follow-up, the 1-year, 2-year and 5-year cumulative incidence of TB in close contacts were 2.15% (95% CI: 1.51%-2.80%), 1.21% (95% CI: 0.93%-1.49%) and 1.11% (95% CI: 0.64%-1.58%), respectively. Individuals with a positive result of MTB infection testing at baseline showed significantly higher cumulative TB incidence as compared to those negatives (3.80% vs. 0.82%, p

• Post-BNT162b2 booster anti-spike IgG titers of healthcare workers were measured. • SARS-CoV-2 exposures and breakthrough infections were recorded during an omicron epidemic. • Post-booster IgG titers were inversely correlated with a SARS-CoV-2 infection risk. • Household exposure was an important source of SARS-CoV-2 infection for healthcare workers. • Exposure with IgG titers of <3,000 AU/mL increased the risk of breakthrough infection. The emergence of omicron variants exhibiting antigenic changes has led to an increase in breakthrough infection among individuals with a wild-type SARS-CoV-2 vaccine booster. The correlation between post-booster spike-specific antibodies and omicron infection risk remains unclear. This prospective cohort study included SARS-CoV-2-naive healthcare workers with three-dose BNT162b2. Post-booster spike-specific IgG and interferon-γ levels were measured. Breakthrough infection was documented during a 10-month omicron-predominant period. Household and healthcare contacts were followed to identify subsequent infections. The IgG titers were additionally measured at the end of follow-up, and the titers at exposure were estimated from the two-point titers. Of 333 participants, 89 developed infection, of whom 37 (41.6 %) were household contacts. Kaplan-Meier curves indicated that higher IgG titers were significantly correlated with lower cumulative infection incidence (p = 0.029), whereas the interferon-γ levels were not (p = 0.926). Multivariate Cox analysis showed that increasing IgG titers were associated with a reduced hazard ratio (HR) of 0.26 (95% CI, 0.12–0.55). Household exposure posed a greater infection risk than healthcare exposure (HRs, 11.24 [6.88–18.40] vs. 2.82 [1.37–5.44]). The difference in geometric mean IgG titers of infected and uninfected participants was significant among household contacts (20,244 AU/mL vs. 13,842 AU/mL, p = 0.031). Estimation of IgG titers at exposure showed a significantly higher infection incidence in those exposed with titers of <3,000 AU/mL than in those with higher titers (79.2 % vs. 32.3 %, p < 0.001). Spike-specific antibodies induced by a wild-type SARS-CoV-2 vaccine booster are suggested to be effective in protecting against omicron infection. Household exposure would be a significant source of infection for hospital healthcare workers. [ABSTRACT FROM AUTHOR]

Background: Individuals in close contact with active pulmonary tuberculosis (TB) patients showed a high risk of recent infection and, once infected, higher risk of developing active TB in the following years post-exposure. But the peak time of active disease onset is unclear. This study aims to estimate post exposure TB incidence risk among close contacts to provide reference for clinical and public health strategies. Methods: We searched PubMed, Web of Science, and EMBASE for articles published until December 1, 2022. The incidence rates were quantitatively summarized by means of meta-analysis using the random-effect model. Results: Of the 5616 studies, 31 studies included in our analysis. For baseline close contacts results, the summarized prevalence of Mycobacterium tuberculosis (MTB) infection and active TB was found to be 46.30% (95% CI: 37.18%-55.41%) and 2.68% (95% CI: 2.02%-3.35%), respectively. During the follow-up, the 1-year, 2-year and 5-year cumulative incidence of TB in close contacts were 2.15% (95% CI: 1.51%-2.80%), 1.21% (95% CI: 0.93%-1.49%) and 1.11% (95% CI: 0.64%-1.58%), respectively. Individuals with a positive result of MTB infection testing at baseline showed significantly higher cumulative TB incidence as compared to those negatives (3.80% vs. 0.82%, p < 0.001). Conclusions: Individuals with close contact to active pulmonary TB patients are bearing significant risk of developing active TB, particularly within the first-year post-exposure. Population with recent infections should be an important priority for active case finding and preventive intervention worldwide. [ABSTRACT FROM AUTHOR]

• A booster dose effectiveness is remains unclear against Omicron BA.2 subvariant. • Updating evidence for university students is essential to improve their vaccine acceptance. • A booster dose reduced the infection rate of close contacts during BA.2 dominancy. • Vaccine effectiveness tended to decrease in BA.2 dominancy than in BA.1 dominancy. Although the COVID-19 Omicron BA.1 subvariant was initially predominant, the BA.2 subvariant has now replaced it. Effectiveness of a booster dose vaccination for BA.2 remains unclear among university students. We enrolled 562 Japanese university students who became a close contact and underwent polymerase chain reaction testing. We compared infection rates and cumulative incidence rates of severe fever among the students according to the COVID-19 vaccine doses received between BA.1-dominant (January 1-March 31, 2022) and BA.2-dominant (April 1-July 31, 2022) periods. Infection rates for BA.1 were 32% with 3 doses, 49% with 2 doses, and 68% in the unvaccinated (P =.008). The odds ratio (OR) for infection following 3 doses during BA.1 was 0.46 (95% confidence interval [CI] = 0.25-0.82, P =.009). Infection rates for BA.2 were 45% with 3 doses, 62% with 2 doses, and 64% in the unvaccinated (P =.02). The OR for infection following 3 doses during BA.2 was 0.50 (95% CI = 0.31-0.82, P =.006). Effectiveness of vaccine for BA.2 tended to decrease for both 3 (45% vs 32%, P =.06) and 2 doses (62% vs 49%, P =.07) compared with those for BA.1. Booster dose effectiveness tended to decrease but remained significant against BA.2 subvariant predominancy among Japanese university students. [ABSTRACT FROM AUTHOR]

Background: COVID-19 vaccination was expected to reduce SARS-CoV-2 transmission, but the relevance of this effect remains unclear. We aimed to estimate the effectiveness of COVID-19 vaccination of the index cases and their close contacts in reducing the probability of SARS-CoV-2 transmission. Methods: Transmission of SARS-CoV-2 infection was evaluated in two cohorts of adult close contacts of COVID-19 confirmed cases (social and household settings) by COVID-19 vaccination status of the index case and the close contact, from April to November 2021 in Navarre, Spain. The effects of vaccination of the index case and the close contact were estimated as (1–adjusted relative risk) × 100%. Results: Among 19,631 social contacts, 3257 (17%) were confirmed with SARS-CoV-2. COVID-19 vaccination of the index case reduced infectiousness by 44% (95% CI, 27–57%), vaccination of the close contact reduced susceptibility by 69% (95% CI, 65–73%), and vaccination of both reduced transmissibility by 74% (95% CI, 70–78%) in social settings, suggesting some synergy of effects. Among 20,708 household contacts, 6269 (30%) were infected, and vaccine effectiveness estimates were 13% (95% CI, −5% to 28%), 61% (95% CI, 58–64%), and 52% (95% CI, 47–56%), respectively. These estimates were lower in older people and had not relevant differences between the Alpha (April-June) and Delta (July-November) variant periods. Conclusions: COVID-19 vaccination reduces infectiousness and susceptibility; however, these effects are insufficient for complete control of SARS-CoV-2 transmission, especially in older people and household setting. Relaxation of preventive behaviors after vaccination may counteract part of the vaccine effect on transmission.

Objective: We aimed to use network meta-analysis to compare the impact of infection risk factors of close contacts with COVID-19, identify the most influential factors and rank their subgroups. It can provide a theoretical basis for the rapid and accurate tracking and management of close contacts. Methods: We searched nine databases from December 1, 2019 to August 2, 2023, which only took Chinese and English studies into consideration. Odd ratios (ORs) were calculated from traditional meta-estimated secondary attack rates (SARs) for different risk factors, and risk ranking of these risk factors was calculated by the surface under the cumulative ranking curve (SUCRA). Results: 25 studies with 152647 participants identified. Among all risk factors, the SUCRA of type of contact was 69.6 % and ranked first. Among six types of contact, compared with transportation contact, medical contact, social contact and other, daily contact increased risk of infection by 12.11 (OR: 12.11, 95 % confidence interval (CI): 6.51–22.55), 7.76 (OR: 7.76, 95 % CI: 4.09–14.73), 4.65 (OR: 4.65, 95 % CI: 2.66–8.51) and 8.23 OR: 8.23, 95 % CI: 4.23–16.01) times, respectively. Overall, SUCRA ranks from highest to lowest as daily contact (94.7 %), contact with pollution subjects (78.4 %), social contact (60.8 %), medical contact (31.8 %), other (27.9 %), transportation contact (6.4 %). Conclusion: The type of contact had the greatest impact on COVID-19 close contacts infection among the risk factors we included. Daily contact carried the greatest risk of infection among six types of contact, followed by contact with pollution subjects, social contact, other, medical contact and transportation contact. The results can provide scientific basis for rapid assess the risk of infection among close contacts based on fewer risk factors and pay attention to high-risk close contacts during management, thereby reducing tracking and management costs.

Patients treated with radionuclide therapy usually require restrictions on certain activities for a period of time following treatment to optimise protection of the public and ensure the legal dose limit is not exceeded. Software may be used to calculate necessary restriction periods for an individual based on longitudinal dose rate measurements from the time of radiopharmaceutical administration. A spreadsheet program has been used for this purpose in Australian hospitals for the last two decades. However, this spreadsheet has a limitation in that it uses an approximation in the calculation of dose from a contact pattern, which affects the calculated restriction period. A computer program called Dorn was developed that provides the same functionality as the spreadsheet but without this approximation. Proffered radiation safety advice from Dorn and the spreadsheet were compared. Advice from the spreadsheet and Dorn were compared for 55 patients who underwent iodine-131 therapy for differentiated thyroid cancer. The restriction periods for caring for infants, close contact with children and sleeping with a partner were typically about 13 h longer in Dorn than in the spreadsheet, but in some cases were over a week shorter or a month longer. If the Dorn program is used clinically in place of the spreadsheet, some patients will enjoy shorter restriction periods and the therapy provider can be more confident in their compliance with regulatory requirements and best practice. Dorn is freely available from https://doi.org/jg5f. [ABSTRACT FROM AUTHOR]

Objective: To analyze clinical differences between a pediatric population with and without confirmed positive close contact for the new coronavirus, to establish the symptoms that define a population currently served in a children's emergency room for which polymerase chain reaction (PCR) collection for SARS-COV-2 is performed, and thus, make clinical and laboratory screening more reliable and applicable in medical routine. Method: Cross-sectional study that characterized 128 children (0-17 years old) who collected PCR for SARS-COV-2 when seen in an emergency room at a private hospital between March and June 2020. Data were collected from the electronic medical record of the researched hospital. Results: Patients positive for close contact with COVID-19 had more diarrhea (P =.03) and less fever (P =.003) and coughing (P =.03). There was no statistically significant difference between the 2 groups on gender distribution, age, isolation of other etiologic agents, chest x-ray abnormalities, or the need for hospitalization. SARS-Cov-2 PCR showed a higher positivity among patients on the close contact positive group (P <.001). Conclusion: As seen in previous research, positive SARS-CoV-2 tests are not required for the pediatric population to be diagnosed with the new coronavirus. Diarrhea should be included in those related to a high suspicion of potential SARS-CoV-2 infection, prompting nasopharyngeal PCR collection. However, fever and cough are unspecific symptoms for SARS-CoV-2 infection and should not be considered as warning signs for parents and, more importantly, for pediatricians to collect screening examinations. [ABSTRACT FROM AUTHOR]

During the Coronavirus disease 2019 pandemic, short-range virus transmission has been observed to have a higher risk of causing infection than long-range virus transmission. However, the roles played by the inhalation and large droplet routes cannot be distinguished in practice. A recent analytical study revealed the predominance of short-range inhalation over the large droplet spray route as causes of respiratory infections. In the current study, short-range exposure was analyzed via computational fluid dynamics (CFD) simulations using a discrete phase model. Detailed facial membranes, including eyes, nostrils, and a mouth, were considered. In CFD simulations, there is no need for a spherical approximation of the human head for estimating deposition nor the "anisokinetic aerosol sampling" approximation for estimating inhalation in the analytical model. We considered two scenarios (with two spheres [Scenario 1] and two human manikins [Scenario 2]), source-target distances of 0.2 to 2 m, and droplet diameters of 3 to 1,500 µm. The overall CFD exposure results agree well with data previously obtained from a simple analytical model. The CFD results confirm the predominance of the short-range inhalation route beyond 0.2 m for expiratory droplets smaller than 50 µm during talking and coughing. A critical droplet size of 87.5 µm was found to differentiate droplet behaviors. The number of droplets deposited on the target head exceeded those exposed to facial membranes, which implies a risk of exposure through the immediate surface route over a short range. [ABSTRACT FROM AUTHOR]

Background: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can be transmitted through direct, indirect, or close contact with infected people by contaminated respiratory droplets or saliva. This study aimed to investigate the epidemiology of coronavirus disease 2019 (COVID-19) and the secondary attack rate (SAR) in the cases’ close contact.Methods: A total of 431 confirmed COVID-19 patients were randomly selected using systematic random sampling from 15 May to 13 June 2020. The required data were extracted from the CORONALAB database of the Center for Disease Control and Prevention (CDC) at Shiraz University of Medical Sciences. Detection of COVID-19 was performed using Real- Time Polymerase Chain Reaction (RT-PCR) and nasopharyngeal swabs. SAR was also calculated for different groups.Results: Among the index cases, 64.27% were male, 24.80% were public sector employees, and 4.87% were admitted to the intensive care unit. In addition, most of them aged 30-39 years. The SAR was 11.56% (95% CI: 9.86% to 13.25%) in the close contacts. Accordingly, the highest SAR was observed among the friends, 19.05% (95% CI: 7.17% to 30.92%), followed by the spouses of COVID-19 cases, 16.67% (95% CI: 10.81% to 22.51%). Furthermore, diabetes (6.03%) and cardiovascular disease (5.1%) were the most common comorbidities among the index cases.Conclusion: The findings suggested that the SAR was relatively lower among the close contacts. Considering the familial and non-familial relationships between the index cases and their close contacts were the major causes of disease transmission. Therefore, it is crucial to conduct tracing for COVID-19 contacts in all cases with whom patients have had close contact.

Background: COVID-19 causes a high death toll, illness, and economic losses. Transmission of the virus occurs from human to human and has spread to more than 200 countries. The purpose of this research is to determine the relationship between close contact and the COVID-19 incident in South Sumatra, Indonesia. Methods: This research used an observational analysis with a cross-sectional design. The population in this study was all COVID-19 patients and those who had close contact with COVID-19 patients in South Sumatra. The data were analyzed using univariate, bivariate, and multivariate tests. The bivariate analysis uses the chi-square test, while the multivariate analysis uses the logistic regression test. Results: The results show that close contact was related to the incidence of COVID-19 with a P value of 0.00 and an odds ratio adjusted (ORAdj) of 3.59 (95% CI: 2.93–4.39) after the variables of record of visiting local transmission areas, record of visiting health facilities, record of contact with suspected cases, and record of contact with confirmed cases were controlled. Conclusion: The transmission of close contact within families such as households was very high. A transmission could occur between a husband and wife and people who lived in the same house and shared plates while eating. To prevent a broader transmission, people who had close contact with COVID-19 needed to be quarantined. We could carry out public health interventions globally to fight against the pandemic based on these results.

COVID-19 vaccination was expected to reduce SARS-CoV-2 transmission, but the relevance of this effect remains unclear. We aimed to estimate the effectiveness of COVID-19 vaccination of the index cases and their close contacts in reducing the probability of SARS-CoV-2 transmission. Transmission of SARS-CoV-2 infection was evaluated in two cohorts of adult close contacts of COVID-19 confirmed cases (social and household settings) by COVID-19 vaccination status of the index case and the close contact, from April to November 2021 in Navarre, Spain. The effects of vaccination of the index case and the close contact were estimated as (1–adjusted relative risk) × 100%. Among 19,631 social contacts, 3257 (17%) were confirmed with SARS-CoV-2. COVID-19 vaccination of the index case reduced infectiousness by 44% (95% CI, 27–57%), vaccination of the close contact reduced susceptibility by 69% (95% CI, 65–73%), and vaccination of both reduced transmissibility by 74% (95% CI, 70–78%) in social settings, suggesting some synergy of effects. Among 20,708 household contacts, 6269 (30%) were infected, and vaccine effectiveness estimates were 13% (95% CI, −5% to 28%), 61% (95% CI, 58–64%), and 52% (95% CI, 47–56%), respectively. These estimates were lower in older people and had not relevant differences between the Alpha (April-June) and Delta (July-November) variant periods. COVID-19 vaccination reduces infectiousness and susceptibility; however, these effects are insufficient for complete control of SARS-CoV-2 transmission, especially in older people and household setting. Relaxation of preventive behaviors after vaccination may counteract part of the vaccine effect on transmission. [ABSTRACT FROM AUTHOR]

IntroductionCoronavirus disease 2019 has become a major global public health concern in December 2019. However, finding and excluding close contacts of COVID-19 infectors is a critical but difficult issue. This study aimed to introduce a new method of epidemiological investigation named space–time companions, which was adopted in Chengdu, China, in November 2021.MethodsAn observational investigation was conducted during a small outbreak of COVID-19 in Chengdu, China in November 2021. A new method of epidemiological investigation called space–time companion was adopted in this outbreak, which was defined as the one who stayed in the same spatiotemporal grid (range: 800 m * 800 m) with the confirmed COVID-19 infector for more than 10 min in the last 14 days. A flow chart was used to describe the screening process of space–time companions in detail and illustrate the space–time companion epidemic management method.ResultsThe COVID-19 epidemic outbreak in Chengdu was effectively controlled for approximately one incubation period (14 days). After four rounds of space–time companions screening, more than 450,000 space–time companions were screened, including 27 COVID-19 infectors. Moreover, in the subsequent rounds of nucleic acid testing for all people in the city, no infected person were found proving the end of this epidemic outbreak.ConclusionThe space–time companion provides a new idea for screening close contacts of the COVID-19 infector and other similar infectious diseases, which can serve as a supplement to traditional epidemiological history surveys to verify and avoid missing close contacts.

Singapore, like many other nations globally, had to contend with significant caseloads arising from the Coronavirus disease (COVID-19) pandemic. This paper focuses on using technology as an intervention for pandemic management. With scant scientific evidence on effective medications and vaccinations (i.e., pharmaceutical interventions) initially, disease containment strategies predominated during the early phases. Non-pharmaceutical interventions were critical in slowing disease transmission and preventing public healthcare institutions from being overwhelmed. Such interventions could be broadly divided into case-based interventions (e.g., contact tracing and quarantining of close contacts) and population-based measures (e.g., mask use and social distancing). The paper describes Singapore’s experience in the operational implementation of contact-based interventions, and illustrates how harnessing the digital edge enabled fast, accurate, resource-efficient, and flexible execution of ground operations. Singapore applied digital technology and developed an integrated system to facilitate issuance and acknowledgement of quarantine orders, submission of COVID-19 test results, and collection of antigen rapid test kits at the population level. Data was obtained from this proprietary centralised, automated platform. The paper demonstrates how such simple, yet elegant systems could have a direct impact on disease transmission in an outbreak setting and on population health. Moving forward, it is recommended that technology and digital solutions feature prominently in work process designs beyond COVID-19 such as in the management of emerging infectious diseases and non-communicable diseases. [ABSTRACT FROM AUTHOR]

Background: COVID-19 causes a high death toll, illness, and economic losses. Transmission of the virus occurs from human to human and has spread to more than 200 countries. This research aims to determine the relationship between close contact and the COVID-19 incident in South Sumatra, Indonesia. Methods: This research used an observational analysis with a cross-sectional design. The population in this study were all COVID-19 patients and those who had close contact with COVID-19 patients in South Sumatra. The data were analyzed using univariate, bivariate, and multivariate tests. The bivariate analysis uses the chi-square test, while the multivariate analysis uses the logistic regression test. Results: The results show that close contact was related to the incidence of COVID-19 with a P value of 0.00 and an odds ratio adjusted (ORAdj) of 3.59 (95% CI: 2.93-4.39) after the variables of record of visiting local transmission areas, the record of visiting health facilities, the record of contact with suspected cases, and record of contact with confirmed cases were controlled. Conclusion: The transmission of close contact within families, such as households, was very high. A transmission could occur between a husband and wife and people who lived in the same house and shared plates while eating. To prevent a broader transmission, people who had close contact with COVID-19 needed to be quarantined. Based on these results, we could carry out public health interventions globally to fight against the pandemic. [ABSTRACT FROM AUTHOR]

Background: COVID-19 pandemic is a global problem. One of the risk factors for COVID-19 is close contact, which has a greater risk of being confirmed because virus transmission generally occurs directly through droplets. Based on regional risk zoning mapping, Purwakarta District is categorized as a moderate risk zone, and most of the confirmed cases are caused by a history of close contact. Still, people with a history of close contact only sometimes become established patients. This study aimed to determine the relationship between close contact status and the incidence of COVID-19 in the Purwakarta district year 2020. Method: This study used observational analysis and a cross-sectional study design. The research data is secondary data from the Purwakarta Regency Health Office. Purposive sampling was used to select 2,650 people for the study. The data analysis method used is chi-square. Results: According to the respondents' characteristics, most are in their early adulthood (26.8 %) and male (52.3 %). According to bivariate analysis, there is a p-value = 0.002 relationship between close contact status and the incidence of COVID-19. People with close contact status are 1.040 times more likely than people who do not have close contact status to get COVID-19 (95 % CI = 1.013-1.069). Conclusion: Close contact status is a risk factor for COVID-19 transmission in Purwakarta Regency during 2020. [ABSTRACT FROM AUTHOR]

Background: SARS-CoV-2 transmission has been reported to be associated with close contact with infected individuals. However, the mechanistic pathway for transmission in close contact settings is unclear. Our objective was to identify, appraise and summarise the evidence from studies assessing the role of close contact in SARS-CoV-2 transmission. Methods: This review is part of an Open Evidence Review on Transmission Dynamics of SARS-CoV-2. We conduct ongoing searches using WHO Covid-19 Database, LitCovid, medRxiv, PubMed and Google Scholar; assess study quality based on the QUADAS-2 criteria and report important findings on an ongoing basis. Results: We included 278 studies: 258 primary studies and 20 systematic reviews. The settings for primary studies were predominantly in home/quarantine facilities (39.5%) and acute care hospitals (12%). The overall reporting quality of the studies was low-to-moderate. There was significant heterogeneity in design and methodology. The frequency of attack rates (PCR testing) varied between 2.1-75%; attack rates were highest in prison and wedding venues, and in households. The frequency of secondary attack rates was 0.3-100% with rates highest in home/quarantine settings. Three studies showed no transmission if the index case was a recurrent infection. Viral culture was performed in four studies of which three found replication-competent virus; culture results were negative where index cases had recurrent infections. Eighteen studies performed genomic sequencing with phylogenetic analysis – the completeness of genomic similarity ranged from 77-100%. Findings from systematic reviews showed that children were significantly less likely to transmit SARS-CoV-2 and household contact was associated with a significantly increased risk of infection. Conclusions: The evidence from published studies demonstrates that SARS-CoV-2 can be transmitted in close contact settings. The risk of transmission is greater in household contacts. There was a wide variation in methodology. Standardized guidelines for reporting transmission in close contact settings should be developed.

With the development of the novel coronavirus disease 2019 (COVID-19) epidemic and the increase in cases, as a potential source of infection, the risk of close contact has gradually increased. However, few studies have analyzed the tracking and management of cross-regional personnel. In this study, we hope to understand the effectiveness and feasibility of existing close contact management measures in Chengdu, so as to provide a reference for further prevention and control of the epidemic. The close contact management mode and epidemiological characteristics of 40,425 close contacts from January 22, 2020, to March 1, 2022, in Chengdu, China, were analyzed. The relationship with index cases was mainly co-passengers (57.58%) and relatives (7.20%), and the frequency of contact was mainly occasional contact (70.39%). A total of 400 (0.99%) close contacts were converted into cases, which were mainly found in the first and second nucleic acid tests (53.69%), and the contact mode was mainly by sharing transportation (63.82%). In terms of close contact management time, both the supposed ((11.93 ± 3.00) days vs. (11.92 ± 7.24) days) and actual ((13.74 ± 17.47) days vs. (12.60 ± 4.35) days) isolation times in Chengdu were longer than those of the outer cities (P

Background: SARS-CoV-2 transmission has been reported to be associated with close contact with infected individuals. However, the mechanistic pathway for transmission in close contact settings is unclear. Our objective was to identify, appraise and summarise the evidence from studies assessing the role of close contact in SARS-CoV-2 transmission. Methods: This review is part of an Open Evidence Review on Transmission Dynamics of SARS-CoV-2. We conduct ongoing searches using WHO Covid-19 Database, LitCovid, medRxiv, PubMed and Google Scholar; assess study quality based on the QUADAS-2 criteria and report important findings on an ongoing basis. Results: We included 278 studies: 258 primary studies and 20 systematic reviews. The settings for primary studies were predominantly in home/quarantine facilities (39.5%) and acute care hospitals (12%). The overall reporting quality of the studies was low-to-moderate. There was significant heterogeneity in design and methodology. The frequency of attack rates (PCR testing) varied between 2.1-75%; attack rates were highest in prison and wedding venues, and in households. The frequency of secondary attack rates was 0.3-100% with rates highest in home/quarantine settings. Three studies showed no transmission if the index case was a recurrent infection. Viral culture was performed in four studies of which three found replication-competent virus; culture results were negative where index cases had recurrent infections. Eighteen studies performed genomic sequencing with phylogenetic analysis – the completeness of genomic similarity ranged from 77-100%. Findings from systematic reviews showed that children were significantly less likely to transmit SARS-CoV-2 and household contact was associated with a significantly increased risk of infection. Conclusions: The evidence from published studies demonstrates that SARS-CoV-2 can be transmitted in close contact settings. The risk of transmission is greater in household contacts. There was a wide variation in methodology. Standardized guidelines for reporting transmission in close contact settings should be developed.

Objectives: Close contact with patients with COVID-19 is speculated to be the most common cause of viral transmission, but the pathogenesis of COVID-19 by close contact remains to be elucidated. In addition, despite olfactory impairment being a unique complication of COVID-19, the impact of SARSCoV-2 on the olfactory cell lineage has not been fully validated. This study aimed to elucidate close-contact viral transmission to the nose and lungs and to investigate the temporal damage in the olfactory receptor neuron (ORN) lineage caused by SARS-CoV-2. Methods: Syrian hamsters were orally administered SARS-CoV-2 nonvariant nCoV-19/JPN/TY/WK521/2020 as direct-infection models. On day 3 after inoculation, infected and uninfected hamsters were housed in the same cage for 30 minutes. These uninfected hamsters were subsequently assigned to a close-contact group. First, viral presence in the nose and lungs was verified in the infection and close-contact groups at several time points. Next, the impacts on the olfactory epithelium, including olfactory progenitors, immature ORNs, and mature ORNs were examined histologically. Then, the viral transmission status and chronological changes in tissue damage were compared between the direct-infection and close-contact groups. Results: In the close-contact group, viral presence could not be detected in both the nose and lungs on day 3, and the virus was identified in both tissues on day 7. In the direct-infection group, the viral load was highest in the nose and lungs on day 3, decreased on day 7, and was no longer detectable on day 14. Histologically, in the direct-infection group, mature ORNs were most depleted on day 3 (p <0.001) and showed a recovery trend on day 14, with similar trends for olfactory progenitors and immature ORNs. In the close-contact group, there was no obvious tissue damage on day 3, but on day 7, the number of all ORN lineage cells significantly decreased (p <0.001). Conclusion: SARS-CoV-2 was transmitted even after brief contact and subsequent olfactory epithelium and lung damage occurred more than 3 days after the trigger of infection. The present study also indicated that SARS-CoV-2 damages all ORN lineage cells, but this damage can begin to recover approximately 14 days post infection. [ABSTRACT FROM AUTHOR]

With the spread of the Coronavirus disease 2019 (COVID-19), missing learning opportunities due to COVID-19 has been raised as a major concern for university education. We aimed to examine the effectiveness of a booster dose of COVID-19 vaccines among Japanese university students during the spread of the Omicron variant. We enrolled 249 students who became a close contact and 294 COVID-19-infected students though the Hiroshima University COVID-19 registration system. Infection rates of people in close contact with sick individuals and symptoms of infected students were examined. Close contacts who had received a booster dose showed a significantly lower infection rate (31%) compared with those with two doses (50%, p = 0.02) and the unvaccinated (71%, p = 0.002). Age- and sex-adjusted odds ratios of receipt of a booster dose vs. two doses and unvaccinated were 0.40 (95% confidence interval [CI], 0.23–0.70, p = 0.001) and 0.44 (95% CI, 0.25–0.77, p = 0.004), respectively. The incidence of severe fever (38.5°C or higher) was significantly less prevalent in those with a booster dose (16%) compared with two doses (40%, p = 0.002) and those who were unvaccinated (75%, p < 0.0001). Booster doses reduced infection rates among close-contact students and can help students to avoid missing learning opportunities. [ABSTRACT FROM AUTHOR]

JinJian Yao,1,&ast; Hangfei Wang,2,&ast; Weiling Yu,3,&ast; Yimin Li,4 Zhiqian Luo,2 Biao Wu,5 Wei Zhang,6 Xiaoran Liu,2 Chuanzhu Lv6,7 1Emergency Center, Hainan General Hospital Affiliated to Hainan Medical University, Haikou, Hainan, People’s Republic of China; 2Department of Emergency, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan, People’s Republic of China; 3Oncology Department, Haikou City People’s Hospital, Haikou, Hainan, People’s Republic of China; 4Department of General Surgery, Yang Jiang Hospital of Qiongzhong, Qiongzhong, Hainan, People’s Republic of China; 5Department of Infectious Disease, Hainan General Hospital Affiliated to Hainan Medical University, Haikou, Hainan, People’s Republic of China; 6Emergency and Trauma College of Hainan Medical University, Haikou, Hainan, People’s Republic of China; 7Key Laboratory of Emergency and Trauma, Ministry of Education of Hainan Medical University, Haikou, Hainan, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Xiaoran LiuDepartment of Emergency, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan, People’s Republic of ChinaTel +8613118901829Email liuxiaoran3192@163.comChuanzhu LvKey Laboratory of Emergency and Trauma, Ministry of Education of Hainan Medical University, Haikou, Hainan, People’s Republic of ChinaTel +8617789830771Email lvchuanzhu677@126.comIntroduction: Close contacts of individuals with COVID-19 may directly gain immunity against SARS-CoV-2 despite lacking a detectable infection. This study examined SARS-CoV-2-specific antibodies levels based on gender, age, and exposure source in close contacts of individuals with COVID-19 and compared antibody levels to patients with an asymptomatic or symptomatic COVID-19 infection.Methods: Two patients had confirmed COVID-19 infections at a community hospital in Qiongzhong, Hainan province. Contact tracing identified all individuals in the community who had been exposed to the two patients during the 14 days before their diagnoses. Close contacts quarantined for 14 days, underwent two SARS-CoV-2 tests, and were screened for SARS-CoV-2-specific antibodies at 7 and 12 weeks after the end of quarantine. SARS-CoV-2-specific antibody levels for the close contacts were compared to those for patients with an asymptomatic or symptomatic COVID-19 infection at 7 and 12 weeks after their diagnoses.Results: Contact tracing identified 10,573 individuals in the community, including 360 (3.4%) close contacts. At 7 weeks, 30 (8.33%) close contacts were positive for SARS-CoV-2-specific antibodies (IgG, n = 26 [7.22%]; IgM, n = 4 [1.11%]), which were lower than the proportion of patients with an asymptomatic (IgG, 100% [12/12]) or symptomatic (IgG, 93.6% [44/47]) COVID-19 infection. SARS-CoV-2-specific IgM antibody levels were significantly higher in close contacts who were exposed through a relative compared to a doctor–patient relationship (P = 0.032). SARS-CoV-2-specific IgG antibody levels were significantly higher in close contacts aged < 18 years vs 18– 64 years (P = 0.014). At 12 weeks, SARS-CoV-2-specific IgG antibody levels among close contacts were significantly lower than among patients with an asymptomatic (P = 0.004) or symptomatic COVID-19 infection (P < 0.001).Conclusion: Immune protection conferred by close contact is short term and unlikely to contribute to herd immunity. There remains an unmet public health need for mass vaccination of populations to increase levels of protective antibodies and achieve and maintain herd immunity.Keywords: SARS-CoV-2, COVID-19, antibody, close contact

ObjectivesClose contact with patients with COVID-19 is speculated to be the most common cause of viral transmission, but the pathogenesis of COVID-19 by close contact remains to be elucidated. In addition, despite olfactory impairment being a unique complication of COVID-19, the impact of SARS-CoV-2 on the olfactory cell lineage has not been fully validated. This study aimed to elucidate close-contact viral transmission to the nose and lungs and to investigate the temporal damage in the olfactory receptor neuron (ORN) lineage caused by SARS-CoV-2.MethodsSyrian hamsters were orally administered SARS-CoV-2 nonvariant nCoV-19/JPN/TY/WK521/2020 as direct-infection models. On day 3 after inoculation, infected and uninfected hamsters were housed in the same cage for 30 minutes. These uninfected hamsters were subsequently assigned to a close-contact group. First, viral presence in the nose and lungs was verified in the infection and close-contact groups at several time points. Next, the impacts on the olfactory epithelium, including olfactory progenitors, immature ORNs, and mature ORNs were examined histologically. Then, the viral transmission status and chronological changes in tissue damage were compared between the direct-infection and close-contact groups.ResultsIn the close-contact group, viral presence could not be detected in both the nose and lungs on day 3, and the virus was identified in both tissues on day 7. In the direct-infection group, the viral load was highest in the nose and lungs on day 3, decreased on day 7, and was no longer detectable on day 14. Histologically, in the direct-infection group, mature ORNs were most depleted on day 3 (p

Background: SARS-CoV-2 transmission has been reported to be associated with close contact with infected individuals. However, the mechanistic pathway for transmission in close contact settings is unclear. Our objective was to identify, appraise and summarise the evidence from studies assessing the role of close contact in SARS-CoV-2 transmission. Methods: This review is part of an Open Evidence Review on Transmission Dynamics of SARS-CoV-2. We conduct ongoing searches using WHO Covid-19 Database, LitCovid, medRxiv, PubMed and Google Scholar; assess study quality based on the QUADAS-2 criteria and report important findings on an ongoing basis. Results: We included 278 studies: 258 primary studies and 20 systematic reviews. The settings for primary studies were predominantly in home/quarantine facilities (39.5%) and acute care hospitals (12%). The overall reporting quality of the studies was low-to-moderate. There was significant heterogeneity in design and methodology. The frequency of attack rates (PCR testing) varied between 2.1-75%; attack rates were highest in prison and wedding venues, and in households. The frequency of secondary attack rates was 0.3-100% with rates highest in home/quarantine settings. Three studies showed no transmission if the index case was a recurrent infection. Viral culture was performed in four studies of which three found replication-competent virus; culture results were negative where index cases had recurrent infections. Eighteen studies performed genomic sequencing with phylogenetic analysis – the completeness of genomic similarity ranged from 77-100%. Findings from systematic reviews showed that children were significantly less likely to transmit SARS-CoV-2 and household contact was associated with a significantly increased risk of infection. Conclusions: The evidence from published studies demonstrates that SARS-CoV-2 can be transmitted in close contact settings. The risk of transmission is greater in household contacts. There was a wide variation in methodology. Standardized guidelines for reporting transmission in close contact settings should be developed.

面对传染病规模大、受影响人数多、大人群的流行病学调查和密切接触者排查困难等问题, 研究运用互联网及大数据技术, 针对确诊患者、活动轨迹等关键组成要素, 通过实体识别、关系路径建立等, 构建面向大人群的传染病密切接触者排查模型, 解决传统流行病学及密切接触者调查方法难以应对大人群调查的问题。该模型形成了一种高效的确诊患者到密切接触者追踪方法, 可有效提升区域内公共卫生应急领域的专业能力和防控成效。 [ABSTRACT FROM AUTHOR]

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Those who are found in close contact with COVID-19 patients and are also negative by polymerase chain reaction (PCR) test may act without waiting for the incubation period to elapse, can become infectious and spread the infection. A machine learning model that can evaluate the risk of infection in close contact with COVID-19 patients within the incubation period from the contact status reported from the index case was created using posterior probabilities. To confirm actual predictability, a verification test was conducted on 169 new close contacts, and the machine learning model was compared with four experienced healthcare workers for the predictability. In a verification test, 33 of the 169 contacts were infected with COVID-19 during the incubation period, and 13 of 33 were negative on initial PCR test, after that the disease developed and their PCR test became positive. The machine learning model predicted the eventual infection in 12 of 13 patients who had negative results on the initial PCR test. In the verification test, the sensitivity of the machine learning model was 0.879 and the specificity was 0.588. The mean−standard deviation of the sensitivity and the specificity of the four health care workers was 0.568 (0.230) for sensitivity and 0.689 (0.103) for specificity. If it is possible to convey that individual risk of infection, the close contact may take suppressive action during the incubation period regardless of the result of the initial PCR test, thereby preventing secondary spread of infection. [ABSTRACT FROM AUTHOR]

Understanding human contact behavior plays a crucial role in improving the design of indoor environments, for example, by enhancing thermal comfort, workplace performance and productivity, and controlling infection transmission. Although baseline information for indoor environmental design is available, data on person-to-person contact behavior are limited, especially in populations of diverse nationalities, genders, and age ranges. In this study, we used high-resolution video cameras to collect close contact data for five consecutive school days in a multinational graduate school student office in Japan with a reserved cultural background. We characterized human close-contact behavior using stochastic interactions in terms of interpersonal distance, assortativity, posture, duration, and frequency of contact in a multinational population. Our results showed a remarkable difference compared to the study results from person-to-person contact behavior in an ethnically homogenous population. The interpersonal distance averaged 0.75 m, and the close contact frequency was notably lower, but the close contact duration was significantly longer. Nationality showed stronger homophily. We considered the degree centrality measures of the nodes in the observed networks. The observed contact network links were dense with high reciprocity. High contact heterogeneity was observed in twenty-five percent of the nodes. These data can be used to improve targeted epidemiological analyses for indoor occupant health decision-making, and infection spread prevention strategies. • Person-to person contact patterns in indoor populations are far from homogenous. • Close contact frequency is notably lower, while the contact duration is longer in a diverse indoor population. • Interpersonal distance (IPD) is significantly wider than the IPD observed in comparable ethnically homogenous populations. • Assortative mixing and indoor co-presence of occupants influences close contact. [ABSTRACT FROM AUTHOR]

Background: SARS-CoV-2 transmission has been reported to be associated with close contact with infected individuals. However, the mechanistic pathway for transmission in close contact settings is unclear. Our objective was to identify, appraise and summarise the evidence from studies assessing the role of close contact in SARS-CoV-2 transmission. Methods: This review is part of an Open Evidence Review on Transmission Dynamics of SARS-CoV-2. We conduct ongoing searches using WHO Covid-19 Database, LitCovid, medRxiv, PubMed and Google Scholar; assess study quality based on the QUADAS-2 criteria and report important findings on an ongoing basis. Results: We included 278 studies: 258 primary studies and 20 systematic reviews. The settings for primary studies were predominantly in home/quarantine facilities (39.5%) and acute care hospitals (12%). The overall reporting quality of the studies was low-to-moderate. There was significant heterogeneity in design and methodology. The frequency of attack rates (PCR testing) varied between 2.1-75%; attack rates were highest in prison and wedding venues, and in households. The frequency of secondary attack rates was 0.3-100% with rates highest in home/quarantine settings. Three studies showed no transmission if the index case was a recurrent infection. Viral culture was performed in four studies of which three found replication-competent virus; culture results were negative where index cases had recurrent infections. Eighteen studies performed genomic sequencing with phylogenetic analysis – the completeness of genomic similarity ranged from 77-100%. Findings from systematic reviews showed that children were significantly less likely to transmit SARS-CoV-2 and household contact was associated with a significantly increased risk of infection. Conclusions: The evidence from published studies demonstrates that SARS-CoV-2 can be transmitted in close contact settings. The risk of transmission is greater in household contacts. There was a wide variation in methodology. Standardized guidelines for reporting transmission in close contact settings should be developed.

Background: Understanding the relative transmissibility of SARS-CoV-2 virus across different contact settings and the possibility of superspreading events is important for prioritizing disease control. Such assessment requires proper consideration of individual level exposure history, which is made possible by contact tracing. Methods: The case-ascertained study in Shandong, China including 97 laboratory-confirmed index cases and 3158 close contacts. All close contacts were quarantined after their last exposure of index cases. Contacts were tested for COVID-19 regularly by PCR to identify both symptomatic and asymptomatic infections. We developed a Bayesian transmission model to the contact tracing data to account for different duration of exposure among individuals to transmission risk in different settings, and the heterogeneity of infectivity of cases. Results: We estimate secondary attack rates (SAR) to be 39% (95% credible interval (CrI): 20–64%) in households, 30% (95% CrI: 11–67%) in healthcare facilities, 23% (95% CrI: 7–51%) at workplaces, and 4% (95% CrI: 1–17%) during air travel. Models allowing heterogeneity of infectivity of cases provided a better goodness-of-fit. We estimated that 64% (95% CrI: 55–72%) of cases did not generate secondary transmissions, and 20% (95% CrI: 15–26%) cases explained 80% of secondary transmissions. Conclusions: Household, healthcare facilities and workplaces are efficient setting for transmission. Timely identification of potential superspreaders in most transmissible settings remains crucial for containing the pandemic.

Abstract Background Previous studies showed that recovered coronavirus disease 2019 (COVID-19) patients can have a subsequent positive polymerase chain reaction (PCR) test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after they are discharged from the hospital. Understanding the epidemiological characteristics of recovered COVID-19 patients who have a re-positive test is vital for preventing a second wave of COVID-19. Methods This retrospective study analyzed the epidemiological and clinical features of 20,280 COVID-19 patients from multiple centers in Wuhan who had a positive PCR test between December 31, 2019, and August 4, 2020. The RT-PCR test results for 4079 individuals who had close contact with the re-positive cases were also obtained. Results In total, 2466 (12.16%) of the 20,280 patients had a re-positive SARS-CoV-2 PCR test after they were discharged from the hospital, and 4079 individuals had close contact with members of this patient group. All of these 4079 individuals had a negative SARS-CoV-2 PCR test. Conclusions This retrospective study in Wuhan analyzed the basic characteristics of recovered COVID-19 patients with re-positive PCR test and found that these cases may not be infectious.

Background and Objectives: At present, investigation of extensive contact of tuberculosis (TB) patients’ families is not a routine part of TB control efforts in most countries. This study was conducted to evaluate the effective contacts of TB cases to assess the potential risk of transmission and its determinants in their families. Methods: In this cross-sectional study, registered TB cases in Kerman, Iran provided information about their family size and type and frequency of unprotected effective contacts with their families from 2014 to 2015. The unprotected effective contact was defined using the Centre for Disease Control (CDC) classification (2005) based on the close, frequent, and long-term contact of TB cases. The demographic variables and the frequency of effective contact were analyzed using a logistic regression model with Stata version 12 with 95% confidence intervals. Results: Overall, among 407 contacts of 74 TB cases, 73% had effective contacts. Having an effective contact was significantly higher among females (Adjusted Odds Ratio (AOR)=5.1; 95% CI:1.9-13.7); those with a lower education level (AOR=4.0; 95% CI: 1.4-15.1), lower income (AOR=7.7; 95% CI: 2.2-27.0), and a house size ≤80 m2 (AOR=16.6; 95% CI: 5.1-54.3); Afghan patients (AOR=30.2; 95% CI: 3.4-272.1); and those living in the rural areas (AOR=4.9; 95% CI: 1.8-21.9). Conclusion: It seems that unprotected effective contact with the family members is high among TB patients, which can be a serious concern for the control of TB in this area. Reducing these unprotected effective contacts through educating patients and their families besides screening of the family members can help the health sector to decrease the burden of TB in Iran.

The SARS-CoV-2 B.1.617.2 (Delta) variant flared up in late May in Guangzhou, China. Transmission characteristics of Delta variant were analysed for 153 confirmed cases and two complete transmission chains with seven generations were fully presented. A rapid transmission occurred in five generations within 10 days. The basic reproduction number (R0) was 3.60 (95% confidence interval: 2.50–5.30). After redefining the concept of close contact, the proportion of confirmed cases discovered from close contacts increased from 43% to 100%. With the usage of a yellow health code, the potential exposed individuals were self-motivated to take a nucleic acid test and regained public access with a negative testing result. Facing the massive requirement of screening, novel facilities like makeshift inflatable laboratories were promptly set up as a vital supplement and 17 cases were found, with 1 pre-symptomatic. The dynamic adjustment of these three interventions resulted in the decline of Rt from 5.00 to 1.00 within 9 days. By breaking the transmission chain and eliminating the transmission source through extending the scope of the close-contact tracing, health-code usage and mass testing, the Guangzhou Delta epidemic was effectively contained. [ABSTRACT FROM AUTHOR]

COVID-19 is currently the biggest threat that challenges all of humankind's health and property. One promising and effective way to control the rapid spreading of this infection is searching for primary close contacts of the confirmed cases. In response, we propose COVID-19 Tracer, a low-cost passive searching system to find COVID-19 patients' close contacts. The main idea is utilizing ubiquitous WiFi probe requests to describe the location similarity, which is then achieved by two designed range-free judgment indicators: location similarity coefficient and close contact distance. We have carried out extensive experiments in a school office building, and the experimental results show an average accuracy of more than 98%, demonstrating our system's effectiveness in judging close contacts. Last but not least, we have developed a prototype system for a school building to find potential close contacts. [ABSTRACT FROM AUTHOR]

Many factors might affect SARS-CoV-2 transmission, but their relevance is not well established. The objectives were to assess the secondary attack rate (SAR) and the risk factors for SARS-CoV-2 transmission from confirmed index cases to their close contacts in household and non-household settings. This cohort study included the close contacts of SARS-CoV-2 infected cases confirmed between May and December 2020 in Navarre, Spain. Epidemiological and clinical variables of the index case and close contacts were collected. The SAR was calculated, and the independent effect of each variable on the transmission risk was evaluated by logistic regression. A total of 59,900 close contacts of 20,048 index cases were studied, and 53.6% were household contacts. SAR was 34.9% overall, 46.8% in household contacts and 21.1% in non-household contacts. The risk of transmission was higher in household setting (adjusted odds ratio (aOR) 2.96, 95% CI 2.84–3.07), from symptomatic index cases (aOR 1.50, 95% CI 1.43–1.58), immigrants (aOR 1.44, 95% CI 1.36–1.52), and increased with age. A higher susceptibility of close contacts was associated with 5–14 years of age, immigrants (aOR 1.54), very low or low-income level (aOR 1.27, and aOR, 1.17, respectively), healthcare work (aOR 1.21), and diagnosis of diabetes (aOR 1.14, 95%CI 1.03–1.25), chronic kidney disease (aOR 1.18, 95%CI 1.04–1.35), hypertension (aOR 1.11, 95% CI 1.03–1.19), and severe obesity (aOR 1.18, 95% CI 1.00–1.38). Transmission increased progressively from May to September 2020 as the B.1.177 variant became dominant. The risk of SARS-CoV-2 infection was considerable among close contacts of infected persons. The higher risk associated with household contacts, immigrants, older index cases, close contacts with lower income level and comorbidities should be considered to address preventive interventions. [ABSTRACT FROM AUTHOR]

COVID-19 has threatened human lives. Countries have implemented various interventions such as vaccination, mask-wearing, body temperature screening, and isolation. However, the effectiveness of single and combined interventions has not yet been accurately analyzed. In this study, an improved SEIR model considering both real human indoor close contact behaviors and susceptibility to COVID-19 was established. Taking Hong Kong as an example, a quantitative assessment of the relationship between the efficiency of single and combined interventions and implementation time and intensity was carried out. The results showed that the infection risk (one-hour close contact with an infected person) of COVID-19 of students, workers, and non-workers/non-students was 3.1%, 8.7%, and 13.6%, respectively. Workplace closures were more effective among built environment interventions. If mask-wearing was mandatorily required in schools, workplaces, supermarkets, shopping centers, and public transport, COVID-19 could not be totally restricted. Workers should be prioritized for vaccination, followed by non-workers/non-students and students. Among all interventions, reducing close contact rate and increasing vaccination rate were better interventions. There was no COVID-19 outbreak (basic reproduction number R0 = 1) if the close contact reduction rate was 59.9% or the vaccination rate reached 89.5%. The results may provide scientific support for COVID-19 prevention and control. [ABSTRACT FROM AUTHOR]

During the coronavirus disease 2019 (COVID-19) pandemic, maintaining adequate staffing in healthcare facilities is important to provide a safe work environment for healthcare workers (HCWs). Japan's early return-to-work (RTW) program may be a rational strategy at a time when there is an increased demand for the services of HCWs. We assessed whether the early RTW program for HCWs who have been in close contact with a COVID-19 case in our hospital was justified. Close contacts were identified according to the guidance document of the World Health Organization. HCWs who met all of the following conditions were eligible to apply to an early RTW program: (1) difficult to replace with another HCW, (2) received the third dose of a COVID-19 mRNA vaccine, (3) a negative COVID-19 antigen test before each work shift, and (4) consent from relevant HCWs and their managers to participate in the program. Between January and March 2022, 256 HCWs were identified as close contacts (median age, 35 years; 192 female). Thirty-seven (14%) secondary attack cases of COVID-19 were detected. Among 141 HCWs (55%) who applied to the early RTW program, nurses and physicians comprised about three-quarters of participants, with a higher participation rate by physicians (78%) than nurses (59%). Eighteen HCWs tested positive for COVID-19 by the sixth day after starting the early RTW program. No COVID-19 infection clusters were reported during the observation period. These findings suggest that the early RTW program for COVID-19 close contacts was a reasonable strategy for HCWs during the Omicron wave. [ABSTRACT FROM AUTHOR]

In Italy, during the second epidemic wave of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rapid antigenic (Ag) test at point-of-care (POCT) station were employed to quickly evaluate large numbers of swabs. We collected data of all children who underwent the Ag test in our hospital. All positive patients were recalled to perform reverse transcription polymerase chain reaction. A total of 2133 tests were collected over 1 month. Clinical data of 1941 children (median age = 3.7 years) were analyzed: 1343 (69.2%) patients complained of symptoms, 594 (30.6%) had a history of close contact with SARS-CoV-2-positive individuals. Among symptoms reported, acute rhinitis was the most frequent (67.9%), followed by cough (42.6%) and fever (31.5%). Among all tests, 95.8% resulted negative, 4.2% positive: 37/89 were confirmed. In confirmed cases, fever (56.2% vs 32.2%; P =.041) and gastrointestinal symptoms (18.8% vs 6.25%; P =.041) were significantly more frequent compared with negative children. The use of POCT for Ag test seems appropriate for SARS-CoV-2 screening in the pediatric population. In children, fever and gastrointestinal symptoms may constitute red flags of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Head orientations directly determine movement directions of exhaled pathogen‐laden droplets, while there is a lack of research about the effect of the infected person's head orientations on respiratory disease transmission during close contact. This work experimentally investigated the effect of different head orientations of an infected person (IP) on the bioaerosol deposition on a healthy person (HP) during close contact. Also, the effectiveness of PV flow in reducing bioaerosol deposition on the HP under the IP's different head orientations was investigated. Bacteriophage T3 was employed to represent viruses inside the cough‐generated aerosols. The bioaerosol depositions on different locations of the HP's upper body (chest, shoulder, and neck) and face (chin, mucous membranes, cheek, and forehead) were characterized by a cultivation method. Results showed that the IP's different head orientations resulted in significantly different deposition density on the HP. PV flow could reduce the bioaerosol deposition remarkably for most cases investigated. The effectiveness of PV flow in reducing deposition on the HP was significantly affected by the IP's head orientations. Findings suggest that changing head orientations can be a control measure to reduce the bioaerosol deposition. Personalized ventilation can be a potential method to reduce the bioaerosol deposition on the HP. [ABSTRACT FROM AUTHOR]

To explain the observed phenomenon that most SARS‐CoV‐2 transmission occurs indoors whereas its outdoor transmission is rare, a simple macroscopic aerosol balance model is developed to link short‐ and long‐range airborne transmission. The model considers the involvement of exhaled droplets with initial diameter ≤50 µm in the short‐range airborne route, whereas only a fraction of these droplets with an initial diameter within 15 µm or equivalently a final diameter within 5 µm considered in the long‐range airborne route. One surprising finding is that the room ventilation rate significantly affects the short‐range airborne route, in contrast to traditional belief. When the ventilation rate in a room is insufficient, the airborne infection risks due to both short‐ and long‐range transmission are high. A ventilation rate of 10 L/s per person provides a similar concentration vs distance decay profile to that in outdoor settings, which provides additional justification for the widely adopted ventilation standard of 10 L/s per person. The newly obtained data do not support the basic assumption in the existing ventilation standard ASHRAE 62.1 (2019) that the required people outdoor air rate is constant if the standard is used directly for respiratory infection control. Instead, it is necessary to increase the ventilation rate when the physical distance between people is less than approximately 2 m. [ABSTRACT FROM AUTHOR]

Objective: This study was aimed at investigating the effectiveness of inactivated COVID-19 vaccines against the Delta variant. Methods: We performed a retrospective cohort study of close contacts of people with laboratory-confirmed SARS-CoV-2 infections in Hunan province, China, from July to August 2021. Mixed-effect logistic regression was used to estimate vaccine effectiveness (VE), and analyze the effects of the vaccination status of index cases and the exposure risk level on VE estimation. Results: A total of 1,685 close contacts of 126 index cases were included; 835 (49.6%) had received two doses of inactivated vaccines, and the median interval between the 2nd dose and exposure was 48 days (IQR: 41 to 56 days). Full vaccination was defined as two doses at least 14 days before exposure. Adjusted VE estimates for full vaccination were 54.8% (95% CI: 7.7 to 77.9) and 68.4% (95% CI: 8.5 to 89.1) against symptomatic and moderate-tosevere COVID-19, respectively. VE for inactivated vaccines was difficult to observe if index cases had been fully vaccinated. The estimated VE with respect to infection protection was lower among household than non-household contacts. Conclusion: Complete primary immunization of two-dose inactivated COVID-19 vaccines protected against SARS-CoV-2 Delta variant infection. Infection risk was higher among vaccinated household contacts than vaccinated nonhousehold contacts. [ABSTRACT FROM AUTHOR]