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Strongyloides stercoralis is a soil‐transmitted helminth which is distributed predominately throughout tropical and subtropical regions and is considered a neglected tropical disease. Due to low larval output, traditional microscopic methods lack sensitivity, especially in areas of low endemicity. Serological assays present an opportunity to study the epidemiology of S. stercoralis in areas of low endemicity such as Jamaica. The current study evaluated the seroprevalence of S. stercoralis in a selected subpopulation in Jamaica. An analysis was conducted on 311 archived serum samples previously submitted for investigating viral infections during a fever epidemic between 2014 and 2015. Randomly selected, anonymized sera were tested for the presence of S. stercoralis IgG antibodies using the AccuDiag Strongyloides IgG ELISA Kit. Data including age, sex, clinical diagnosis, and the geographic location of sample submission were recorded to delineate trends in demographic variables. The seropositivity rate of S. stercoralis was 15.43%. The rate among females and males was 16.45% and 14.47%, respectively (χ2 = 0.2339, p = 0.629). The highest rate was found in middle adulthood (31–50 years) (26.53%; 13/49). The seroprevalence of S. stercoralis was significantly highest in a rural Regional Health Authority (33.33%; 14/42) and least within an urban Health Authority (9.71%; 17/175). Exposure to S. stercoralis appears to be highest in the rural Regional Health Authorities with an island‐wide exposure rate of 15.43%. The rapid ELISA testing method for the detection of IgG antibodies to S. stercoralis used in this study may be useful as part of a combined approach to elucidate the epidemiology of this soil‐transmitted parasite in Jamaica. [ABSTRACT FROM AUTHOR]

To clarify the epidemiology of enterovirus D68 (EV‐D68), an enterovirus rarely identified in the 20th century, we performed seroepidemiological analysis against EV‐D68 using sera collected in 1976, 1985, 1990, 1999, 2009, and 2019, as well as Yamagata isolate (EVD68/Yamagata.JPN/2023‐89), in Yamagata, Japan. The neutralizing antibody (Ab)‐positive rates for those under 20 years old were 61.0%, 82.5%, 84.3%, 46.7%, 50.5%, and 67.9%, in each year, whereas the rates for those above 20 years old were between 93.4% and 99.1%. Generally, geometric mean titers (GMTs）increased with age among children and the total GMT in each year was 25.4, 49.2, 37.2, 30.8, 29.5, and 33.9, from 1976 to 2019, respectively. The findings in this Yamagata‐based study showed that the seroprevalence of EV‐D68 over the last four decades has increased with age among children, as a susceptible group, and then reaches a plateau of over approximately 80% among adults. This study clearly revealed that EV‐D68 was stably transmitted among children in the 20th century, when EV‐D68 detection was quite rare. [ABSTRACT FROM AUTHOR]

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Background & Aims: COVID-19 is one of the most significant diseases of recent years, spreading globally through human-to-human transmission. The purpose of this study is to investigate the seroepidemiological titers of SARS-CoV-2 antibodies in the urban population of Urmia city based on samples from individuals who referred to local laboratories. This study aims to provide new insights into the epidemiologic behavior of COVID-19 in society. Materials & Methods: Approximately 4,000 people who referred to the laboratories of Urmia participated in this study. Plasma levels of IgM and IgG antibodies were measured, and the frequency of positive antibody titers in the entire population was calculated based on demographic characteristics such as age and gender. IgM and IgG levels were compared between the two genders. Additionally, IgM and IgG levels were compared across age groups: children and adolescents under 20 years old; young adults (20–40 years old); middle-aged individuals (40-60 years old); and the elderly (60 years and older). Results: In this study, the frequencies of IgM+ and IgG+ were determined as well as the frequency of (IgM/IgG+) among the participants. Plasma levels of IgG were not different between women and men, whereas IgM levels were higher in women than in men. The plasma levels of antibodies in the age groups of children and young people were lower than in the middle-aged and elderly age groups. Conclusion: The findings of this study highlight that older adults and individuals with confirmed infections mounted a stronger antibody response. Additionally, the differences in IgM levels between genders warrant further research to explore their potential clinical significance.

Chikungunya and dengue are arboviral diseases transmitted by mosquitoes that have been increasingly recognized as public health concerns in Sub-Saharan Africa. Several studies conducted in Nigeria and other West African countries have revealed the seroprevalence burden and cocirculation of antibodies against mosquito-borne infections, thereby revealing a significant burden and clinical outcome complexities that have largely gone undetected. The current research study has important implications for disease surveillance, prevention strategies, and healthcare planning in Nigeria and other Sub-Saharan countries. A cross-sectional study was conducted on 871 outpatients and pregnant women from three regions of Nigeria. CHIKV and DENV immunoblot molecular diagnostic assays were used to analyze the serum samples for the presence of arboviral antibody serological markers IgG (Mikrogen Diagnostik, Germany) with DENV nonstructural protein 1 and DENV Equad and CHIKV virus-like particles (VLPs), according to the manufacturer’s instructions. A total of 871 participants were recruited from three geographical regions in Nigeria. Among them, 17.5% (152/871) were from Abia (southern Nigeria), 34.4% (300/871) were from Kaduna (northern Nigeria), and 48.1% (419/871) were from Nasarawa (central Nigeria). The ages of the participants ranged from 0 months to 80 years, with a mean age of 36.6 years. Of the 871 subjects, 71.0% (619/871) were female, and 29.0% (252/871) were male. The overall cohort detectable antibody seropositivity against CHIKV was 64.9% (565/871), 95% CI (61.74–68.06); DENV, 44.7% (389/871), 95% CI (41.41–47.99); and CHIKV-DENV cocirculation antibodies, 31.6% (95% CI 29–35). This study highlighted the unpredictably high seroprevalence, expansion, magnitude, and undetected burden of chikungunya and dengue in Nigeria.

Toxoplasma gondii is one of the most common zoonotic parasites worldwide, with infections in humans as well as in all mammals, including dromedaries, that affect reproductive health, leading to malformations and abortions. In the current study, we estimated, for the first time in Tunisia, the seroprevalence of T. gondii antibodies and its associated risk factors in dromedaries (Camelus dromedarius) using the enzyme-linked immunosorbent assay (ELISA) technique. A total of 248 sera samples were collected from dromedaries living in Médenine and Tataouine governorates, South Tunisia. The overall seroprevalence of T. gondii was estimated to be 29.8 ± 2.9% (74/248) with a significantly higher seroprevalence rate in dromedaries from Médenine (52.5 ± 7.9%; 21/40) compared to Tataouine (25.5 ± 3%; 53/208); it was also higher in dromedaries kept in intensive farming systems (55 ± 11.1%; 11/20) compared to extensive systems (27.6 ± 3%; 63/228), in non-pregnant females (39 ± 4%; 57/146) compared to pregnant ones (16.7 ± 3.7%; 17/102), and in those in contact with cats (66.7 ± 8.6%; 20/30) compared to those with no contact with cats (24.8 ± 2.9%; 54/218). The present study should be followed by others to explore the role of dromedaries in the epidemiological cycle of T. gondii in Southern Tunisia. [ABSTRACT FROM AUTHOR]

Seroepidemiological characteristics of human papillomavirus (HPV) in community residents reflect natural infection and can guide the reform of vaccination programs. A population‐based serological survey was conducted in Guangdong Province. Serum anti‐HPV IgG antibody levels were determined by an ELISA. Neutralizing antibodies against HPV6, 11, 16, and 18 were detected via a pseudovirus‐based neutralization assay (PBNA). A total of 5122 serum samples were collected from community residents, including 1989 males and 3133 females, in three cities of Guangdong Province. The rate of HPV IgG antibody positivity in females was 5.39% (95% CI: 4.6–6.2), which was greater than that in males (2.36%; 95% CI: 1.7–3.1). HPV IgG antibodies were more frequently detected in females aged 51–60 years (11.30%; 95% CI: 7.6–16.0), whereas in males, the detection increased with age and reached 4.94% (95% CI: 2.8–6.9) in the group aged ≥71 years. The seropositivity of neutralizing antibodies against HPV6 and 11 was greater than that against HPV16 and 18. The serum neutralizing antibody titers in individuals who received three doses of a vaccine were 7‐ to 12‐fold greater than those in individuals who did not receive the vaccine. The neutralizing antibody titers slightly decreased within 40 months and ranged from 0.038 to 0.057 log ED50 per month. A moderate consistency between the HPV ELISA and PBNA results was observed (Kappa score = 0.49, r = 0.249, 0.635, 0.382, and 0.466 for HPV6, 11, 16, and 18, respectively). The HPV seropositivity rate among healthy residents of Guangdong Province was found to be low among children and adolescents and to increase with age. The serum neutralizing antibody titers were significantly greater in the vaccine group than that in the control group, and this difference persisted over time, which indicated promising protection against HPV infection. [ABSTRACT FROM AUTHOR]

Simple Summary: Several literature reviews of arboviruses in Nigeria have demonstrated a high prevalence of chikungunya and dengue antibodies in individuals with either febrile or non-febrile illness. The current study reveals a substantial burden of undetected arboviral cocirculating antibodies of these mosquito-borne diseases in the country. This underscores the importance of incorporating multiplex diagnostic testing and surveillance efforts to accurately determine the full extent of the arbovirus disease burden in Nigeria and Sub-Saharan Africa. Chikungunya and dengue are arboviral diseases transmitted by mosquitoes that have been increasingly recognized as public health concerns in Sub-Saharan Africa. Several studies conducted in Nigeria and other West African countries have revealed the seroprevalence burden and cocirculation of antibodies against mosquito-borne infections, thereby revealing a significant burden and clinical outcome complexities that have largely gone undetected. The current research study has important implications for disease surveillance, prevention strategies, and healthcare planning in Nigeria and other Sub-Saharan countries. A cross-sectional study was conducted on 871 outpatients and pregnant women from three regions of Nigeria. CHIKV and DENV immunoblot molecular diagnostic assays were used to analyze the serum samples for the presence of arboviral antibody serological markers IgG (Mikrogen Diagnostik, Germany) with DENV nonstructural protein 1 and DENV Equad and CHIKV virus-like particles (VLPs), according to the manufacturer's instructions. A total of 871 participants were recruited from three geographical regions in Nigeria. Among them, 17.5% (152/871) were from Abia (southern Nigeria), 34.4% (300/871) were from Kaduna (northern Nigeria), and 48.1% (419/871) were from Nasarawa (central Nigeria). The ages of the participants ranged from 0 months to 80 years, with a mean age of 36.6 years. Of the 871 subjects, 71.0% (619/871) were female, and 29.0% (252/871) were male. The overall cohort detectable antibody seropositivity against CHIKV was 64.9% (565/871), 95% CI (61.74–68.06); DENV, 44.7% (389/871), 95% CI (41.41–47.99); and CHIKV-DENV cocirculation antibodies, 31.6% (95% CI 29–35). This study highlighted the unpredictably high seroprevalence, expansion, magnitude, and undetected burden of chikungunya and dengue in Nigeria. [ABSTRACT FROM AUTHOR]

Monitoring trachoma transmission with antibody data requires characterization of decay in IgG to Chlamydia trachomatis antigens. In a 3-year longitudinal cohort in a high-transmission setting, we estimated a median IgG half-life of 3 years and a seroreversion rate of 2.5 per 100 person-years (95% confidence interval, 1.6–3.5). Clinical Trials Registration NCT02754583. [ABSTRACT FROM AUTHOR]

Little is known about the frequency of Zika virus (ZIKV) infections in Sudan. The aim of this study was to obtain data on the prevalence of ZIKV infections and the immunity of the population in the country. To this end, 198 sera obtained between December 2012 and January 2013 in different regions in Sudan were examined for neutralizing antibodies against ZIKV, dengue virus (DENV), and yellow fever virus (YFV). The sera were non-randomly selected. The neutralization titers were compared with each other and with the WHO 1st International Standard for anti-Asian lineage Zika virus antibody. Twenty-six sera neutralized ZIKV. One-third of these sera had higher neutralization titers against ZIKV than against DENV-2 and -3. Two sera showed higher neutralization titers than the WHO standard for ZIKV antibodies. These data suggest occasional ZIKV infections in Sudan. The low percentage of sera in this cohort that neutralized ZIKV indicates that, in the study period, the population was susceptible to ZIKV infection. [ABSTRACT FROM AUTHOR]

Serosurveys are a key resource for measuring severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) population exposure. A growing body of evidence suggests that asymptomatic and mild infections (together making up over 95% of all infections) are associated with lower antibody titers than severe infections. Antibody levels also peak a few weeks after infection and decay gradually. We developed a statistical approach to produce estimates of cumulative incidence from raw seroprevalence survey results that account for these sources of spectrum bias. We incorporate data on antibody responses on multiple assays from a postinfection longitudinal cohort, along with epidemic time series to account for the timing of a serosurvey relative to how recently individuals may have been infected. We applied this method to produce estimates of cumulative incidence from 5 large-scale SARS-CoV-2 serosurveys across different settings and study designs. We identified substantial differences between raw seroprevalence and cumulative incidence of over 2-fold in the results of some surveys, and we provide a tool for practitioners to generate cumulative incidence estimates with preset or custom parameter values. While unprecedented efforts have been launched to generate SARS-CoV-2 seroprevalence estimates over this past year, interpretation of results from these studies requires properly accounting for both population-level epidemiologic context and individual-level immune dynamics.

This study aimed to evaluate the seroprevalence of Bordetella pertussis and persistence of antibodies following vaccination. We recruited 6060 healthy subjects from five provinces of China during 2017–2018. Serum IgG antibodies against pertussis toxin (anti-PT IgG) and filamentous hemagglutinin (anti-FHA IgG), and serum IgA antibodies against pertussis toxin (anti-PT IgA) were measured by ELISA. Geometric mean concentration (GMC), seropositivity rate, and recent infection rate were calculated. Among 0–6 years-olds, the anti-PT IgG, anti-PT IgA, and anti-FHA IgG GMCs were 6.4 IU/ml (95% CI 6.1–6.8), 2.8 IU/ml (95% CI 2.7–2.8), and 13.3 IU/ml (95% CI 12.4–14.2), respectively. The anti-PT IgG GMC increased in accordance with the primary vaccination series (4–6 months) and the toddler booster (18–24 months), but declined thereafter through to age 5 years [4.7 IU/ml (95% CI 4.2–5.4)]. The seropositivity rate of pertussis in >6 year-olds was 9.0% (95% CI 8.1–9.9) and the recent infection rate was 3.3% (95% CI, 2.7–3.8). Recent infection rate began to increase from 6 years of age, with peaks at 9, 20, 40, and ≥60 years of age. The anti-PT IgG GMCs of children aged 0–6 years who were vaccinated with DTaP, DTaP-IPV//PRP～T, and DTaP-Hib were 5.9 IU/ml (95% CI 5.6–6.3), 20.7 IU/ml (95% CI 15.6–27.8), and 11.7 IU/ml (95% CI 7.5–18.1) (p

ABSTRACTThis study employed sero-epidemiological methods to estimate the incidence of pertussis within a healthy population located in eastern China. The aim was to gain deeper insights into the epidemiological characteristics and burden of pertussis within the country. Blood samples were collected from healthy individuals in Jiangsu Province between June 2019 and December 2022. The levels of IgG antibodies against pertussis toxin (anti-PT) and filamentous hemagglutinin (anti-FHA) in the serum were quantitatively measured using enzyme-linked immunosorbent assay (ELISA). Additionally, pertussis case data reported in Jiangsu Province were collected from the China Information System for Disease Control and Prevention and compared with the results of this study. In 2022, the reported incidence of pertussis stood at 1.0 per 100,000 individuals, marking the highest rate observed in the past two decades. Among 1,909 patients examined, the geometric mean concentration (GMC) of anti-PT IgG antibody was 20.2 (18.5–21.9) IU/ml, while that of anti-FHA IgG antibody was 27.0 (25.4–28.7) IU/ml. The IgG-PT and IgG-FHA seropositivity rate (>20.0 IU/ml) was highest in the 1 ~ 2 y old group and decreased rapidly to the lowest in the 3 ~ 4 y old group and then increased gradually with age. The estimated rate of pertussis infection based on seroprevalence was approximately 25,625‐fold higher than the reported notification rate in the ≥15 year age group. Our findings highlight decreased immunity post-vaccination, stressing the importance of additional booster shots for adolescents and adults to maintain immunity and reduce severe illness. Additionally, they offer vital guidance for policymakers to enhance immunization strategies.

Safe and effective typhoid conjugate vaccines (TCVs) are available, but many countries lack the high-resolution data needed to prioritize TCV introduction to the highest-risk communities. Here we discuss seroepidemiology-an approach using antibody response data to characterize infection burden-as a potential tool to fill this data gap. Serologic tests for typhoid have existed for over a hundred years, but only recently were antigens identified that were sensitive and specific enough to use as epidemiologic markers. These antigens, coupled with new methodological developments, permit estimating seroincidence-the rate at which new infections occur in a population-from cross-sectional serosurveys. These new tools open up many possible applications for enteric fever seroepidemiology, including generating high-resolution surveillance data, monitoring vaccine impact, and integrating with other serosurveillance initiatives. Challenges remain, including distinguishing Salmonella Typhi from Salmonella Paratyphi infections and accounting for reinfections. Enteric fever seroepidemiology can be conducted at a fraction of the cost, time, and sample size of surveillance blood culture studies and may enable more efficient and scalable surveillance for this important infectious disease.

BACKGROUND: Racial and ethnic minorities have borne a disproportionate burden from coronavirus disease 2019 (COVID-19). Certain essential occupations, including food processing and farm work, employ large numbers of Hispanic migrant workers and have been shown to carry an especially high risk of infection. METHODS: This observational cohort study measured the seroprevalence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and assessed the risk factors for seropositivity among food processing and farm workers, and members of their households, in North Carolina, USA. Participants completed questionnaires, blood samples were collected, and an enzyme-linked immunosorbent assay was used to assess SARS-CoV-2 seropositivity. Univariate and multi-variate analyses were undertaken to identify risk factors associated with seropositivity, using generalized estimating equations to account for household clustering. FINDINGS: Among the 218 participants, 94.5% were Hispanic, and SARS-CoV-2 seropositivity was 50.0%. Most seropositive individuals did not report a history of illness compatible with COVID-19. Attending church, having a prior history of COVID-19, having a seropositive household member, and speaking Spanish as ones primary language were associated with SARS-CoV-2 seropositivity, while preventive behaviours were not. INTERPRETATION: These findings underscore the substantial burden of COVID-19 among a population of mostly Hispanic essential workers and their households in rural North Carolina. This study contributes to a large body of evidence showing that Hispanic Americans have suffered a disproportionate burden of COVID-19. This study also highlights the epidemiologic importance of viral transmission within the household.

Toxoplasma gondii is one of the most common zoonotic parasites worldwide, with infections in humans as well as in all mammals, including dromedaries, that affect reproductive health, leading to malformations and abortions. In the current study, we estimated, for the first time in Tunisia, the seroprevalence of T. gondii antibodies and its associated risk factors in dromedaries (Camelus dromedarius) using the enzyme-linked immunosorbent assay (ELISA) technique. A total of 248 sera samples were collected from dromedaries living in Médenine and Tataouine governorates, South Tunisia. The overall seroprevalence of T. gondii was estimated to be 29.8 ± 2.9% (74/248) with a significantly higher seroprevalence rate in dromedaries from Médenine (52.5 ± 7.9%; 21/40) compared to Tataouine (25.5 ± 3%; 53/208); it was also higher in dromedaries kept in intensive farming systems (55 ± 11.1%; 11/20) compared to extensive systems (27.6 ± 3%; 63/228), in non-pregnant females (39 ± 4%; 57/146) compared to pregnant ones (16.7 ± 3.7%; 17/102), and in those in contact with cats (66.7 ± 8.6%; 20/30) compared to those with no contact with cats (24.8 ± 2.9%; 54/218). The present study should be followed by others to explore the role of dromedaries in the epidemiological cycle of T. gondii in Southern Tunisia.

Background: Rubella remains a public health challenge in Japan, impeding the attainment of herd immunity. Despite vaccination efforts since 1976, persistent outbreaks reveal a susceptibility gap in male adults born before 1995. Seroepidemiological surveys are pivotal in evaluating population immunity and identifying at-risk groups. Methods: This study aims to pinpoint high-risk areas for potential rubella outbreaks in Japan by merging seroepidemiological data from 2020 with population census information. Various data sources, including spatial demographic data, reported rubella and congenital rubella syndrome (CRS) cases, and traveler lodging statistics, were employed. Geospatial information for Japan's 230,300 small geographic areas was analyzed, and HI (hemagglutination inhibition) titers were examined by age and sex. Seroconversion was defined as an HI titer ≥ 1:32 or 1:16, indicating protective immunity. Geospatial maps illustrated the distribution of susceptible individuals per square kilometer, emphasizing high-risk urban areas like Tokyo and Osaka. Demographic shifts in the working-age population were assessed. Results: Susceptible individuals cluster in densely populated urban centers, persisting despite demographic changes. The study highlights areas at risk of increased susceptibility, particularly with an HI titer cut-off of 1:16. Foreign travelers pose potential rubella importation risks as travel volume to Japan rises. To prevent epidemics and congenital rubella syndrome burden, achieving and sustaining herd immunity in high-risk areas is crucial. Conclusions: This study offers a comprehensive assessment of vulnerability in densely populated Japanese regions. Integrating population statistics with seroepidemiological data enhances our understanding of population immunity, guiding resource allocation for supplementary vaccination planning. To avert rubella epidemics, high-risk locations must bolster indirect protection through herd immunity, ultimately preventing congenital rubella syndrome.

Abstract Background Contagious bovine pleuropneumonia (CBPP) is an economically important infectious disease that is characterized by a variable course and insidious nature. A cross-sectional study was conducted in El Jazeera State, Central Sudan, to determine the seroprevalence and risk factors of CBPP in cattle from seven localities. A total of 218 serum samples were randomly collected from apparently healthy cattle aged older than 6 months between April and May 2021 and were tested serologically using a commercial ELISA kit. Results The overall seroprevalence of CBPP was 50.5% (110/218). Univariate analysis showed a significant difference (p

Rubella remains a public health challenge in Japan, impeding the attainment of herd immunity. Despite vaccination efforts since 1976, persistent outbreaks reveal a susceptibility gap in male adults born before 1995. Seroepidemiological surveys are pivotal in evaluating population immunity and identifying at-risk groups. This study aims to pinpoint high-risk areas for potential rubella outbreaks in Japan by merging seroepidemiological data from 2020 with population census information. Various data sources, including spatial demographic data, reported rubella and congenital rubella syndrome (CRS) cases, and traveler lodging statistics, were employed. Geospatial information for Japan's 230,300 small geographic areas was analyzed, and HI (hemagglutination inhibition) titers were examined by age and sex. Seroconversion was defined as an HI titer ≥ 1:32 or 1:16, indicating protective immunity. Geospatial maps illustrated the distribution of susceptible individuals per square kilometer, emphasizing high-risk urban areas like Tokyo and Osaka. Demographic shifts in the working-age population were assessed. Susceptible individuals cluster in densely populated urban centers, persisting despite demographic changes. The study highlights areas at risk of increased susceptibility, particularly with an HI titer cut-off of 1:16. Foreign travelers pose potential rubella importation risks as travel volume to Japan rises. To prevent epidemics and congenital rubella syndrome burden, achieving and sustaining herd immunity in high-risk areas is crucial. This study offers a comprehensive assessment of vulnerability in densely populated Japanese regions. Integrating population statistics with seroepidemiological data enhances our understanding of population immunity, guiding resource allocation for supplementary vaccination planning. To avert rubella epidemics, high-risk locations must bolster indirect protection through herd immunity, ultimately preventing congenital rubella syndrome. [ABSTRACT FROM AUTHOR]

This is a SARS-CoV-2 seroepidemiological study in a pediatric population (0–16 years) during the BA.5 Omicron predominance period in the Athens metropolitan area. Serum samples were tested for SARS-CoV-2 nucleocapsid antibodies (Abs-N), representing natural infection during three periods of BA.5 predominance: 1 May 2022–31 August 2022 (period A), 1 September 2022–31 December 2022 (period B), and July 2023 (period C). Εpidemiological data were also collected. Additionally, in period C, Abs-N-seronegative samples were tested for SARS-CoV-2 spike antibodies (Abs-S). A total of 878 children were tested (males: 52.6%), with a median age (IQR) of 96 (36–156) months; the number of cases of seropositivity during the three periods were as follows: A: 292/417 (70%), B: 288/356 (80.9%), and C: 89/105 (84.8%), with p < 0.001. SARS-CoV-2 seropositivity increased from period A to C for children 0–1 year (p = 0.044), >1–4 years (p = 0.028), and >6–12 years (p = 0.003). Children > 6–12 years had the highest seropositivity rates in all periods (A: 77.3%, B: 91.4%, and C: 95.8%). A significant correlation of monthly median Abs-N titers with monthly seropositivity rates was detected (rs: 0.812, p = 0.008). During period C, 12/105 (11.4%) Abs-S-seropositive and Abs-N-seronegative samples were detected and total seropositivity was estimated at 96.2% (101/105). The findings of this study indicate a high SARS-CoV-2 exposure rate of children during the BA.5 predominance period and suggest that in future seroepidemiological studies, both antibodies should be tested in Abs-N-seronegative populations. [ABSTRACT FROM AUTHOR]

The Omicron variant is associated with increased transmissibility, but evidence about the impact of Omicron in seropositivity of children is limited. This study aims to evaluate SARS-CoV-2 seroprevalence in children during the different variants' subperiods. A prospective multicenter seroprevalence study was conducted in 7 University public hospitals in Greece from November 2021 to August 2022 (3 subperiods: November 2021-February 2022, March 2022-May 2022, June 2022-August 2022). Children from different age groups, admitted to the hospital or examined in outpatient clinics for reasons other than COVID-19 were enrolled. Neutralizing antibodies (Nabs), anti-Spike (anti-S) and anti-nucleocapsid (anti-N) SARS-CoV-2 IgG in serum were evaluated. A total of 2127 children (males:57,2%; median age:4,8years) were enrolled. Anti-N IgG seropositivity increased from 17,8% in the first sub-period to 40,7% in the second sub-period and then decreased in the third sub-period (36,7%). Anti-S IgG seropositivity appeared to have an increasing trend over the study period, starting from 34,8% and reaching 80,7%. Children aged 1–4 years old have significantly higher anti-N IgG titers compared to children aged 0–1 years old (p < 0,001). Infants have significantly lower anti-S IgG titers compared to all other age groups (p < 0,001). Immunocompromised children and infants have the lowest seropositivity for NAbs. Conclusions During the Omicron period, seropositivity significantly increased, as a result of higher transmissibility. Neonates and infants have lower antibody titers compared to other age groups, while young children aged 1–4 years old present higher antibody titers, suggesting that this age group may mount a higher antibody response. Continuous surveillance seroprevalence studies are needed in children, in order to identify the true extent of SARS-CoV-2 and guide the planning of adequate public health measures. [ABSTRACT FROM AUTHOR]

A seroepidemiological study was conducted in 2018 to assess diphtheria and tetanus antibodies in Guangzhou, China. Diphtheria and tetanus antibody concentrations were measured with an enzyme-linked immunosorbent assay. A total of 715 subjects were enrolled in the study. The overall diphtheria and tetanus toxoid IgG-specific antibody levels were 0.126 IU/mL (95% CI: 0.115, 0.137) and 0.210 IU/mL (95% CI: 0.185, 0.240), respectively; the overall positivity rate was 61.82% (95% CI: 58.14, 65.39) and 71.61% (95% CI: 68.3, 74.92), respectively. The diphtheria and tetanus antibody concentration was decreased by age and increased by doses. The geometric mean concentrations and positivity rate of diphtheria and tetanus antibodies were lowest and below the essential protection level in people over 14 years of age. Compared to children and adolescents, middle-aged people and the aged are at much higher risk of infection with Corynebacterium diphtheriae and Clostridium tetani. The current diphtheria and tetanus immunization schedule does not provide persistent protection after childhood. There is an urgent need to adjust the current immunization schedule. [ABSTRACT FROM AUTHOR]

Introduction: Echinococcus species are zoonotic parasites that cause hydatid disease, affecting humans and animals. The seroprevalence of hydatid disease reflects the level of exposure to this parasite and can be used as an indicator of the burden of the disease in a population. Aim: To determine the seroprevalence of hydatid disease. Materials and Methods: The study was a retrospective observational study conducted at JIPMER hospital, a tertiary care centre located in Puducherry, Southern India. In this study, hydatid serological data from January 2019 to December 2022 were collected in March 2023 and retrospectively analysed in April 2023. All the serum samples that tested positive for Enzyme Linked Immuno Sorbent Assay (ELISA) for echinococcosis during the period from January 2019 to December 2022 were included. The demographic details such as age, gender, place of residence, etc., of the patients whose samples were included were collected from their case records. These samples were then analysed using Microsoft Excel for proportions and percentages. Results: The study showed that the seroprevalence of hydatid disease was 70 (34%) out of 206 samples tested. The seroprevalence was higher in the older age group (>45 years), with 41 (58.6%) cases. It was observed that males and females were almost equally infected, with minor differences in the prevalence of 37 (52.9%) males and 33 (47.1%) females. Conclusion: As the prevalence of hydatid disease in Southern India was unknown, it was observed to be lower when compared to other states of India. This study has provided valuable information on the level of exposure of hydatid disease in the population and will help formulate disease control and prevention strategies.

Introduction: Echinococcus species are zoonotic parasites that cause hydatid disease, affecting humans and animals. The seroprevalence of hydatid disease reflects the level of exposure to this parasite and can be used as an indicator of the burden of the disease in a population. Aim: To determine the seroprevalence of hydatid disease. Materials and Methods: The study was a retrospective observational study conducted at JIPMER hospital, a tertiary care centre located in Puducherry, Southern India. In this study, hydatid serological data from January 2019 to December 2022 were collected in March 2023 and retrospectively analysed in April 2023. All the serum samples that tested positive for Enzyme Linked Immuno Sorbent Assay (ELISA) for echinococcosis during the period from January 2019 to December 2022 were included. The demographic details such as age, gender, place of residence, etc., of the patients whose samples were included were collected from their case records. These samples were then analysed using Microsoft Excel for proportions and percentages. Results: The study showed that the seroprevalence of hydatid disease was 70 (34%) out of 206 samples tested. The seroprevalence was higher in the older age group (>45 years), with 41 (58.6%) cases. It was observed that males and females were almost equally infected, with minor differences in the prevalence of 37 (52.9%) males and 33 (47.1%) females. Conclusion: As the prevalence of hydatid disease in Southern India was unknown, it was observed to be lower when compared to other states of India. This study has provided valuable information on the level of exposure of hydatid disease in the population and will help formulate disease control and prevention strategies. [ABSTRACT FROM AUTHOR]

Background: Babesia ovis, an intraerythrocytic parasite carried by ticks and one of the most common subclinical ovine illnesses, was studied to ascertain its seroprevalence and endemic status in ram and ewe populations in East Azerbaijan Province, Iran, in lambs, yearlings, and adults of over two years of age. Methods: A total of 960 sheep from 10 cities were selected from Jan 2018 to Nov 2019. Blood samples were collected from each animal and tested for the presence of B. ovis antibodies by applying a developed enzyme-linked immunosorbent assay (ELISA) technique. Checkerboard titrations were used to determine the optimal dilution of the antigen using negative and positive control sera. To determine whether the disease is endemically stable, inoculation rates for each age group were also calculated. Correlation coefficients were calculated between age and infection rates and also between age and inoculation rates. Results: The results revealed an average infection rate of 49.4% in East Azerbaijan Province. There was a positive correlation between the age of animals and susceptibility to infection except for lambs and yearlings, whereas there was no meaningful difference in exposure to B. ovis between rams and ewes. The negative correlation between age and inoculation rates indicates increased disease instability with age. Inoculation rate results revealed the endemically instable status of B. ovis in the studied area. Conclusion: High prevalence rates and endemically instable status of the disease suggest demand for vaccine development and implementation of appropriate control measures for ovine babesiosis to mitigate the associated economic losses. [ABSTRACT FROM AUTHOR]

The underestimation of the pertussis burden prompted our study to investigate the prevalence of recent pertussis infection, its associated factors, and antibody titer changes in the same individuals in Vietnam. Two cross-sectional surveys were conducted in Nha Trang in 2017 and Quang Ngai in 2019, representing high- and low-vaccine-coverage areas, respectively. Serum anti-pertussis toxin immunoglobulin-G (anti-PT IgG) ≥ 62.5 IU/mL by ELISA indicated infection in the previous 12 months. In Nha Trang, the participants of the 2017 survey were followed up in 2019. Logistic regression was used to determine the odds ratios for the characteristics associated with anti-PT IgG ≥ 62.5. The age-stratified prevalence in patients aged >2 years ranged from 2.1% (age 26–35) to 9.6% (3–5) in Nha Trang (2017) and from 7.2% (age 26–35) to 11.4% (6–15) in Quang Ngai. The prevalence tended to be higher in Quang Ngai across all age groups. Cough, recent antibiotic use, and smoking in Nha Trang were positively associated with an anti-PT IgG of ≥62.5, and having been diagnosed with pertussis and persistent cough with paroxysms/whoop in Quang Ngai were positively associated with an anti-PT IgG of ≥62.5. No nasopharyngeal swabs were positive for Bordetella pertussis using real-time PCR. The geometric mean of the IgG titer ratio from 2019 to 2017 was 1.45 in the paired samples. This study emphasizes Bordetella pertussis circulation across all age groups in both low- and high-vaccine-coverage settings in Vietnam, underscoring the need for continuous and standardized surveillance for a comprehensive understanding of its epidemiology. [ABSTRACT FROM AUTHOR]

Background Seroepidemiologic studies of human tularemia have been conducted throughout the northern hemisphere. The purposes of this study were (1) to provide an overview of Francisella tularensis seroprevalence data, and (2) to generate an estimate of the proportion of study participants whose infection remained subclinical. Methods We conducted a systematic review of F tularensis seroprevalence studies according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We searched PubMed, Embase, and Web of Science covering the period from 1951 to 2023. Results The weighted pooled seroprevalence among 44 486 participants recruited in 52 studies was 3.7% (95% confidence interval [CI], 2.7–5.1). Reported seroprevalences ranged between 0.2% and 31.3%. Occupational activities associated with an increased likelihood of exposure (risk ratio, 3.51 [95% CI, 3.2–3.86]) and studies from North America versus Europe and Asia (4.53 [4.15–4.94]) were associated with significantly increased seropositive rates. Twenty-eight data sets (47%) reported clinical information on a total of 965 seropositive participants. The weighted pooled estimate for subclinical seropositivity was 84.4% (95% CI, 72.9%–991.7%). Studies from F tularensis type A areas (risk ratio, 0.37 [95% CI,.27–.51) and studies from sites where pulmonary tularemia prevailed (0.38 [.28–.51]) reported lower subclinical seropositivity rates than studies from type B areas and from areas of predominance of (ulcero)glandular or oropharyngeal tularemia, respectively. Conclusions Throughout the northern hemisphere, only a small proportion of study participants showed serologic evidence of exposure to F tularensis. Eight of 10 seropositive participants had no historical evidence of past clinical tularemia. [ABSTRACT FROM AUTHOR]

Bovine viral diarrhea virus (BVDV) is one of the most important pathogens of the reproductive systems that have a significant socioeconomic impact on the dairy industry. A cross-sectional study was conducted on 17 randomly selected farms out of 133 registered dairy farms in Holeta, a town in the Walmera district of Ethiopia. The study aimed to detect BVDV antigen-positive animals and investigate the seroprevalence of BVDV infection. A total of 337 serum samples were collected from selected farms with no history of BVDV vaccination. The indirect enzyme-linked immunosorbent assay (I-ELISA) test was the screening test used to detect antibodies against BVDV. In contrast, antigencapture ELISA was used for the detection of BVDV antigens in seronegative animals. A logistic regression model was used to assess the association between potential predictors and BVDV exposure. The overall animal level seroprevalence was 15.4%, and 64.7% of the herds had at least one seropositive animal. From 285 seronegative animals, one animal (0.4%) was found positive for BVDV antigen. The same animal was found positive in a double check 21 days later. In this study, cows with a history of abortion (OR = 6.3; 95% CI: 1.61 -13.1), history of repeated breeding (OR = 7; 95% CI: 2.5 - 14.3), animals managed intensively (OR = 4.6; 95% CI: 1.6 - 13.0) and multiparous cows (OR = 3.6; 95% CI: 1.5 - 8.9) had higher proportion of seroreactors in their respective comparison category (p<0.05). Besides, cows with a history of congenital defective calve birth (OR = 15.2; 95% CI: 3.2 - 73.6), adult age groups (OR = 2.9; 95% CI: 1.0-7.9), and cows bred both artificially and natural mating (OR = 4.6; 95% CI: 1.7 - 12.6) were statistically associated with BVDV seropositivity (p<0.05). In conclusion, this report demonstrated the presence of persistently infected (PI) dairy cattle in Ethiopia. Thus, the findings warrant the need for immediate control intervention that involves both screening and culling of PI animals and vaccination. [ABSTRACT FROM AUTHOR]

Coxiella burnetii is the agent of Q fever, a disease that poses risks to public health and damages livestock. We discovered the circulation of C. burnetii for the first time in Paraguay, based on the seropositivity of a flock of >300 sheep. The animals were tested by IFA for anti-C. burnetii antibodies and by SAM for anti-Leptospira spp. antibodies, an important differential diagnosis for reproductive disorders in sheep in Paraguay. C. burnetii seropositivity was determined in 45%, in contrast to Leptospira spp. which had no reactive samples. Cases of miscarriage and fetal resorption were associated with high seropositivity titers. This study suggests the circulation of a unique genotype in the country and an imminent risk to public health, since in addition to being highly transmissible and infectious to humans, Q fever is still not a cause for concern on the part of government and health agencies in the country.

ABSTRACTToxoplasma gondii is a highly prevalent pathogen causing zoonotic infections with significant public health implications. Yet, our understanding of long-term consequences, associated risk factors, and the potential role of co-infections is still limited. Seroepidemiological studies are a valuable approach to address open questions and enhance our insights into T. gondii across human populations. Here, we present substantial advancements to our previously developed T. gondii multiplex serology assay, which is based on the immunodominant antigens SAG1 and P22. While our previous bead-based assay quantified antibody levels against multiple targets in a high-throughput fashion requiring only a small sample volume, impaired assay characteristics emerged in sample dilutions beyond 1:100 and when being transferred to magnetic beads. Both are now critical for inclusion in large-scale seroprevalence studies. Using the truncated versions, SAG1D1 and P22trunc, significantly enhanced signal-to-noise ratios were achieved with almost perfect concordance with the gold-standard Sabin–Feldman dye test. In sample dilutions of 1:100, the diagnostic accuracy of SAG1D1 and P22trunc reached sensitivities (true positive rates) of 98% and 94% and specificities (true negative rates) of 93% and 95%, respectively. Importantly, performance metrics were reproducible in a 1:1,000 sample dilution, using both magnetic and nonmagnetic beads. Thresholds for seropositivity were derived from finite mixture models and performed equally well as thresholds by receiver operating characteristic analysis. Our improved multiplex serology assay is therefore able to generate robust and reproducible performance metrics under various assay conditions. Inclusion of T. gondii antibody measurements with other pathogens, in multiplex serology panels will allow for large-scale seroepidemiological research.IMPORTANCEToxoplasma gondii is a pathogen of significant public health concern due to its widespread prevalence and zoonotic potential. However, our understanding of key aspects, such as risk factors for infection and disease, potential outcomes, and their trends, remains limited. Seroepidemiological studies in large cohorts are invaluable for addressing these questions but remain scarce. Our revised multiplex serology assay equips researchers with a powerful tool capable of delivering T. gondii serum antibody measurements with high sensitivity and specificity under diverse assay conditions. This advancement paves the way for the integration of T. gondii antibody measurements into multi-pathogen multiplex serology panels, promising valuable insights into public health and pathogen interactions.

Abstract Objective To assess SARS-CoV-2 antibody prevalence and titers in people living with HIV (PLWHIV) on antiretroviral treatment (ART) enrolled at a tertiary reference hospital in Mexico. Methods Two plasma aliquots per person, used for HIV viral load follow-up between 01/2020 and 09/2021, were used to assess total anti-N and neutralizing SARS-CoV-2 antibodies. Sociodemographic, clinical, and SARS-CoV-2 exposure risk information were collected. The risk associated with SARS-CoV-2 exposure and associations with antibody titers were analyzed with logistic, Cox, and linear multivariable models. Results 803 PLWHIV participated; 233 had detectable SARS-CoV-2 antibodies (prevalent cases), and 132 seroconverted (incident cases). Overall, the adjusted prevalence was 46.45%, with an incidence rate of 3.78 cases/100 person-months. Factors associated with prevalent cases included lower age, location (western zone of Mexico City and the neighboring Mexico State), use of public transport, attendance at meetings without social distancing, and higher CD4 + T cell counts (p

Abstract Background Virginia is a large state in the USA, yet it remains unclear what percentage of the population has had natural COVID-19 infection and whether risk factors for infection have changed over time. Methods Using a longitudinal cohort, from December 2021-July 2022 we performed follow up serology and a questionnaire on 784 individuals from across Virginia who had previously participated in a statewide COVID-19 seroepidemiology study in 2020. Children were also invited to participate and an additional 62 children also completed the study. Serology was performed using Roche nucleocapsid and spike serological assays. Results The majority of participants were white (78.6%), over 50 years old (60.9%), and reported having received COVID-19 vaccine (93.4%). 28.6% had evidence of prior COVID-19 infection (nucleocapsid positive). Reweighted by region, age, and sex to match the Virginia census data, the seroprevalence of nucleocapsid antibodies was estimated to be 30.6% (95% CI: 24.7, 36.6). We estimated that 25–53% of COVID-19 infections were asymptomatic. Infection rates were lower in individuals > 60 years old and were higher in Blacks and Hispanics. Infection rates were also higher in those without health insurance, in those with greater numbers of household children, and in those that reported a close contact or having undergone quarantine for COVID-19. Participants from Southwest Virginia had lower seropositivity (16.2%, 95% CI 6.5, 26.0) than other geographic regions. Boosted vaccinees had lower infection rates than non-boosted vaccinees. Frequenting indoor bars was a risk factor for infection, while frequently wearing an N95 mask was protective, though the estimates of association were imprecise. Infection rates were higher in children than adults (56.5% vs. 28.6%). Infection in the parent was a risk factor for child infection. Spike antibody levels declined with time since last vaccination, particularly in those that were vaccinated but not previously infected. Neutralizing antibody positivity was high (97–99%) for wild type, alpha, beta, gamma, delta, and omicron variants. Neutralizing antibody levels were higher in the follow-up survey compared to the first survey in 2020 and among individuals with evidence of natural infection compared to those without. Conclusions In this longitudinal statewide cohort we observed a lower-than-expected COVID-19 infection rate as of August 2022. Boosted vaccinees had lower infection rates. Children had higher infection rates and infections tracked within households. Previously identified demographic risk factors for infection tended to persist. Even after the omicron peak, a large number of Virginians remain uninfected with COVID-19, underscoring the need for ongoing vaccination strategies.

Abstract Background Toxoplasmosis, an important zoonotic disease, is caused by Toxoplasma gondii. Camels are one of several host species for T. gondii parasites and play an important role in the transmission of T. gondii to humans. Objectives The present study aimed to describe the seroprevalence of T. gondii in dromedary camels (Camelus dromedarius) from three provinces (Fars, Bushehr and Hormozgan), southern Iran first for this host. Methods A total of 180 serum samples were analysed for the presence of anti‐Toxoplasma IgG antibodies using the enzyme‐linked immune‐sorbent assay. Results Our results showed an overall seroprevalence of T. gondii in 15% of animals. Antibodies to T. gondii were found in sera of 27 of 180 dromedary camels from Fars, Bushehr and Hormozgan provinces, southern Iran. Age or the gender of the camel did not significantly affect the seroprevalence (p > 0.05). There was no significant association between herd‐level seroprevalence of T. gondii infection and abortion history, province location residence, history of animal keeping and history of contact with other animals (p > 0.05). Conclusions The results of this study showed the presence of T. gondii antibodies among camels in Southern Iran, which could be a public health concern. According to the prevalence of T. gondii infection in camel, the implementation of control measures to reduce infection in both definitive and intermediate hosts is needed.

In Haiti in 2017, the prevalence of serum vibriocidal antibody titers against Vibrio cholerae serogroup O1 among adults was 12.4% in Cerca-la-Source and 9.54% in Mirebalais, suggesting a high recent prevalence of infection. Improved surveillance programs to monitor cholera and guide public health interventions in Haiti are necessary.

Aim: This study aimed to assess the seroprevalence of SARS-CoV-2 and disease symptoms in Malakand, Pakistan. Materials & method: 623 samples with suspected SARS-CoV-2 were collected from different regions of Malakand and analyzed to detect SARS-CoV-2 IgG antibodies using ELISA. Results: 306 (49.1%) 0 f 623 patients were anti-SARS-CoV-2 IgG reactive, with a higher prevalence in males (75%) than females (25%). In this study, we enrolled two groups, subjects working in a non-medical setting and subjects working in a medical setting. Clinical symptoms were statistically linked with SARS-CoV-2. Four weeks of follow-up analysis of IgG titers in health care workers showed an increase in IgG antibodies titer. Conclusion: This study gives insights into the community-based spread of SARS-CoV-2 infection, associated immunity, and herd immunity in the studied population. This study can provide insights to the government about early vaccination of this population as most of the population is not yet vaccinated.

Background: Patients with kidney disease on Hemodialysis (HD) are susceptible to Coronavirus Disease (COVID-19) due to multiple risk factors. Aim: This study aims to report the prevalence of antibodies against SARS-CoV-2 among patients on hemodialysis before vaccination in Brazil and to compare with clinical, demographic, and laboratory data. Methods: Blood samples from 398 Chronic Kidney Disease (CKD) patients treated in three different private institutions in Rio de Janeiro State, Brazil were submitted to the total anti-SARS-CoV-2 testing. Kidney, liver, and hematological markers were also determined. Respiratory samples were tested by real-time PCR for SARS-CoV-2 RNA and positive samples were subjected to high-throughput sequencing on the MinION device. Results: Overall, anti-SARS-CoV-2 prevalence was 54.5 % (217/398) and two individuals had SARS-CoV-2 RNA with variant B.1.1. High anti-SARS-CoV-2 seroprevalence was found in male gender and those with hospital admission in the last 3-months before the inclusion in the study. Lower red blood cell count was observed in the anti-SARS-CoV-2 seropositive group. High levels of anti-SARS-CoV-2 were found in those who reported symptoms, had low levels of eosinophils and low hematocrit, and who practiced physical activity. Conclusion: High prevalence of anti-SARS-CoV-2 was found in CKD patients before the universal immunization in Brazil suggesting that dialysis patients were highly exposed to SARS-CoV-2.

ABSTRACTThere are limited data on individual risk factors for SARS-CoV-2 infection (including unrecognized infection). In this seroepidemiologic substudy of an ongoing prospective cohort study of community-dwelling adults, participants were thoroughly characterized pre-pandemic. The SARS-CoV-2 infection was ascertained by serology. Among 8,719 participants from 11 high-, middle-, and low-income countries, 3,009 (35%) were seropositive for SARS-CoV-2. Characteristics independently associated with seropositivity were younger age (odds ratio, OR; 95% confidence interval, CI, per five-year increase: 0.95; 0.91–0.98) and body mass index >25 kg/m2 (OR, 95% CI: 1.16, 1.01–1.34). Smoking (as compared with never smoking, OR, 95% CI: 0.83, 0.70–0.97) and COVID-19 vaccination (OR, 95% CI: 0.70, 0.60–0.82) were associated with a reduced risk of seropositivity. Among seropositive participants, 83% were unaware of having been infected with SARS-CoV-2. Seropositivity and a lack of awareness of infection were more common in lower-income countries. The COVID-19 vaccination reduces the risk of SARS-CoV-2 infection (including recognized and unrecognized infections). Overweight or obesity is an independent risk factor for SARS-CoV-2 infection. Infection and lack of infection awareness are more common in lower-income countries.IMPORTANCEIn this large, international study, evidence of SARS-CoV-2 infection was obtained by testing blood specimens from 8,719 community-dwelling adults from 11 countries. The key findings are that (i) the large majority (83%) of community-dwelling adults from several high-, middle-, and low-income countries with blood test evidence of SARS-CoV-2 infection were unaware of this infection—especially in lower-income countries; and (ii) overweight/obesity predisposes to SARS-CoV-2 infection, while COVID-19 vaccination is associated with a reduced risk of SARS-CoV-2 infection. These observations are not attributable to other individual characteristics, highlighting the importance of the COVID-19 vaccination to prevent not only severe infection but possibly any infection. Further research is needed to understand the mechanisms by which overweight/obesity might increase the risk of SARS-CoV-2 infection.

Objective: To assess SARS-CoV-2 antibody prevalence and titers in people living with HIV (PLWHIV) on antiretroviral treatment (ART) enrolled at a tertiary reference hospital in Mexico. Methods: Two plasma aliquots per person, used for HIV viral load follow-up between 01/2020 and 09/2021, were used to assess total anti-N and neutralizing SARS-CoV-2 antibodies. Sociodemographic, clinical, and SARS-CoV-2 exposure risk information were collected. The risk associated with SARS-CoV-2 exposure and associations with antibody titers were analyzed with logistic, Cox, and linear multivariable models. Results: 803 PLWHIV participated; 233 had detectable SARS-CoV-2 antibodies (prevalent cases), and 132 seroconverted (incident cases). Overall, the adjusted prevalence was 46.45%, with an incidence rate of 3.78 cases/100 person-months. Factors associated with prevalent cases included lower age, location (western zone of Mexico City and the neighboring Mexico State), use of public transport, attendance at meetings without social distancing, and higher CD4 + T cell counts (p < 0.05; multivariable logistic model). BNT162b2 vaccination reduced incident cases (Cox adjusted HR = 0.4; p = 0.013). Notably, previously infected and vaccinated individuals showed maximization of neutralizing activity (p < 0.001). No associations between SARS-CoV-2 neutralization and HIV-related variables (CD4 + T cell counts, viral load, number of years in viral suppression, ART regimen) were found in multivariable analysis. Conclusions: SARS-CoV-2 infection was associated with community risk rather than HIV-associated variables in PLWH on ART and clinical follow-up. Antibody neutralization activity in vaccinated participants was maximized with previous SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]

Rubella virus infection can cause vertical transmission to the fetus during pregnancy. In China's Henan province, rubella surveillance needs to be well‐established. In this research, a total of 1933 neonates and 2502 pregnant women were enrolled, and their sera for IgG and IgM antibodies against rubella were tested by chemiluminescence assay. Of 1933 neonates' sera tested, the seropositive of rubella IgG was 68.7%. The seroprevalence of rubella IgM in neonates was 0.4%. 30.9% of neonates had negative results for IgG and IgM antibodies. Two thousand five hundred and two pregnant women participated in the serosurvey, and 79.3% were rubella IgG positive. Rubella IgG seropositivity in pregnant women differed by age and number of births. 0.8% of the pregnant women had positive results for IgM against the rubella virus. The seronegative of rubella IgG and IgM antibodies in pregnant women was 19.8%. Due to the negative rubella‐specific IgG antibody, many neonates remain at risk of rubella virus infection. Rubella virus continues to spread since some neonates and pregnant women with rubella‐specific IgM antibody positive have been detected. Rubella vaccination may be introduced for childbearing‐age women to increase immunity levels against rubella with periodic sero‐surveillance. [ABSTRACT FROM AUTHOR]

Background There is no immunization campaign that currently exist for respiratory syncytial virus (RSV). Seroprevalence studies are critical for assessing epidemiological dynamics before and during an immunization program. A systematic literature review was conducted to summarize the evidence from seroprevalence studies on RSV. Methods A systematic search of age-dependent RSV seroprevalence was conducted using the PubMed database and EMBASE. Age-dependent force of infections (FoI) and the decay rate of immunity were estimated. A mixture finite model was used, estimating the age-dependent disease state and the antibody concentrations in susceptible and infected or recovered populations. Results Twenty-one studies were identified from 15 countries, with studies using enzyme-linked immunosorbent assay being the most represented. Using a catalytic model, the age-dependent force of infection was estimated to be the lowest in infants aged 6 months to 1 year and increased in older age groups. The proportion ever-infected/recovered was estimated to be above 90% by 3 years of age. Conclusions The number of seroprevalence studies covering a broad range of ages are limited. The age-dependent FoI indicated that the risk of infection was greatest among those aged >5 years. Additional data using valid assays are required to describe the transmission dynamics of RSV infection. [ABSTRACT FROM AUTHOR]

Background: Virginia is a large state in the USA, yet it remains unclear what percentage of the population has had natural COVID-19 infection and whether risk factors for infection have changed over time. Methods: Using a longitudinal cohort, from December 2021-July 2022 we performed follow up serology and a questionnaire on 784 individuals from across Virginia who had previously participated in a statewide COVID-19 seroepidemiology study in 2020. Children were also invited to participate and an additional 62 children also completed the study. Serology was performed using Roche nucleocapsid and spike serological assays. Results: The majority of participants were white (78.6%), over 50 years old (60.9%), and reported having received COVID-19 vaccine (93.4%). 28.6% had evidence of prior COVID-19 infection (nucleocapsid positive). Reweighted by region, age, and sex to match the Virginia census data, the seroprevalence of nucleocapsid antibodies was estimated to be 30.6% (95% CI: 24.7, 36.6). We estimated that 25–53% of COVID-19 infections were asymptomatic. Infection rates were lower in individuals > 60 years old and were higher in Blacks and Hispanics. Infection rates were also higher in those without health insurance, in those with greater numbers of household children, and in those that reported a close contact or having undergone quarantine for COVID-19. Participants from Southwest Virginia had lower seropositivity (16.2%, 95% CI 6.5, 26.0) than other geographic regions. Boosted vaccinees had lower infection rates than non-boosted vaccinees. Frequenting indoor bars was a risk factor for infection, while frequently wearing an N95 mask was protective, though the estimates of association were imprecise. Infection rates were higher in children than adults (56.5% vs. 28.6%). Infection in the parent was a risk factor for child infection. Spike antibody levels declined with time since last vaccination, particularly in those that were vaccinated but not previously infected. Neutralizing antibody positivity was high (97–99%) for wild type, alpha, beta, gamma, delta, and omicron variants. Neutralizing antibody levels were higher in the follow-up survey compared to the first survey in 2020 and among individuals with evidence of natural infection compared to those without. Conclusions: In this longitudinal statewide cohort we observed a lower-than-expected COVID-19 infection rate as of August 2022. Boosted vaccinees had lower infection rates. Children had higher infection rates and infections tracked within households. Previously identified demographic risk factors for infection tended to persist. Even after the omicron peak, a large number of Virginians remain uninfected with COVID-19, underscoring the need for ongoing vaccination strategies. [ABSTRACT FROM AUTHOR]

Rift Valley fever (RVF) is a mosquito-borne viral disease that affects a variety of domestic animals, including cattle, sheep, goats, and camels, and has zoonotic potential. Although the rift valley fever virus (RVFV) is usually asymptomatic in camels, it can induce abortion in some pregnant animals. In the current study, a serosurvey was carried out to investigate the prevalence of RVFV antibodies and related risk factors in camels from four Egyptian governorates. A total of 400 serum samples were examined for anti-RVFV antibodies using a competitive enzyme-linked immunosorbent assay (c-ELISA). The results revealed that the overall prevalence of RVF among examined camels was 21.5% and the disease was more prevalent in Kafr ElSheikh governorate in Nile Delta of Egypt. In addition, the age group of camels with more than 5 years (OR=4.49, 95%CI: 1.39–14.49), the female sex (OR=3.38, 95%CI: 1.51–7.58), the emaciated animals (OR=1.52, 95%CI: 0.86–2.66), the summer season’s infection (OR=5.98, 95%CI: 1.79–19.93), the presence of mosquitoes (OR= 2.88, 95%CI: 1.39–5.95), and the absence of mosquitoes control (OR=3.97, 95%CI: 2.09–7.57) were identified as risk factors for RVFV infection. The results of this study support knowledge on the risk factors for RVFV infection and demonstrate that camels raising in Egypt have RVFV antibodies. Quarantine measures or vaccination program should be implemented to reduce the likelihood of RVFV introduction, dissemination among susceptible animals, and ultimately transmission to humans. [ABSTRACT FROM AUTHOR]

Simple Summary: Leptospirosis is a zoonosis of bacterial origin caused by spirochetes of the genus Leptospira. It is distributed worldwide and has a great impact on public health and the agricultural economy. In Latin America, leptospirosis is a neglected tropical disease, despite being infectious, zoonotic, with an acute course, and eventually lethal. In the Brazilian state of Goiás, which is located in the tropical savanna (Cerrado), data on the seroprevalence of equine leptospirosis are scarce and restricted to a few municipalities. Thus, the present study aimed to evaluate the seroprevalence of Leptospira spp. in 294 equine herds in the state of Goiás, Brazil. The results shed light on the significant and widespread prevalence of Leptospira in both farms (72.9%) and horses (61.6%) in Goiás State. These results were indicative of a complex epidemiological landscape characterized by the predominance of serogroups such as Djasiman, Icterohaemorrhagiae, and Australis. Therefore, our findings underscore the critical significance of implementing sanitation measures within the environment and conducting health education initiatives to effectively prevent and control equine leptospirosis within the state, with particular emphasis on the necessity of vaccination. Leptospirosis, caused by Leptospira, is a zoonotic disease that, in horses, is linked to abortions, uveitis, and sporadic occurrences of liver and kidney disease, often resulting in significant economic losses for farmers. Research on the prevalence of leptospirosis in horses in the central-west region of Brazil has been relatively scarce. Thus, the present study aimed to determine the prevalence of leptospirosis in equine herds in the state of Goiás (Central Brazil). Blood samples were collected from 894 equids at 294 randomly selected farms divided into three different strata according to their herd characteristics. The microscopic agglutination test for the detection of anti-Leptospira agglutinins was carried out and the results showed that among the 294 sampled farms, 213 (72.9%; CI 95% 71.7–78.9) had one or more animals positive for leptospirosis, and of the 894 horses sampled, 513 (61.6%; CI 95% 54.3–69.0) were seropositive for leptospirosis. Djasiman, Icterohaemorrhagiae, and Australis were the most prevalent serogroups. The results showed a high prevalence of seropositive animals and a widespread distribution of positive farms in the state of Goiás. Thus, environmental sanitation measures and health education to prevent and control equine leptospirosis in the state are required. [ABSTRACT FROM AUTHOR]

Chagas disease (CD), caused by the parasite Trypanosoma cruzi, is a neglected tropical disease with life-threatening implications. In this study, we conducted a seroepidemiological survey to determine the prevalence and clinical profiles of CD in 217 individuals from an impoverished rural community in Southern Bahia, Brazil. The overall prevalence of CD in the studied community was 0.92%, detected through latent class analysis (LCA). Two individuals tested positive for anti-T. cruzi IgG, both being male farmers. One case was a 22-year-old man born in Camamu, with no evidence of congenital transmission, suggesting other routes of transmission such as vector-borne transmission due to migratory activities. The other case was a 69-year-old man born in São Felipe, who had lived in an adobe/brick house and had a pacemaker due to cardiac involvement caused by CD. The prevalence in this community was lower than expected, given the socioeconomic conditions and environmental factors that contribute to T. cruzi transmission. This could be attributed to the implementation of preventive measures and vector control programs by the Brazilian Government. However, continuous monitoring and surveillance are essential to sustain control efforts and detect any potential re-emergence of the disease. While the overall prevalence was low, the detection of positive cases underscores the need for continued surveillance and control measures in vulnerable populations, such as rural communities. Active surveillance, early diagnosis, and timely treatment are crucial in preventing disease progression and complications, thereby enhancing the effectiveness of screening and treatment programs. [ABSTRACT FROM AUTHOR]

Enterovirus A71 (EV-A71) is a significant hand-foot-mouth disease (HFMD) etiology. The inactivated EV-A71 vaccines were approved in China in 2016. However, the seroprevalence of EV-A71 after the vaccine application and its potential association with the EV-A71 epidemic in the population are rarely studied. In this study, we analyzed the incidence of EV-A71 infection and seroepidemiology in Guangzhou City, China. From 2019 to 2021, 167,920 clinically confirmed HFMD cases were reported in Guangzhou. In 6,868 enterovirus-positive samples, Coxsackievirus A6 and Coxsackievirus A16 were dominant genotypes, and only 3 EV-A71-positive samples were detected, highlighting the deficient epidemic activity of EV-A71. Microneutralization assay was performed on 1,000 representative serum samples. Notably, the seroprevalence and geometric mean titer (GMT) decreased significantly in 2020, and that in the < 3-year age group were increased and even higher than that in 3–5-year age group in 2019 and 2021, which was contrary to our previous surveillance result and other studies in Guangzhou. Furthermore, a moderate decline of GMT level was observed following the vaccination, but the seropositive serums were still detected for 49 months after second immunization, suggesting the long-term persistence of the immunity. Our seroepidemiology study revealed relatively higher neutralizing antibody activity in the susceptible population after the EV-A71 vaccine was adopted in 2016 in Guangzhou. It may be one of the reasons for the lower epidemic activity of EV-A71 in Guangzhou from 2019 to 2021.

Background: We aimed to measure the seroprevalences and levels of anti-SARS-CoV-2 IgG in children, unvaccinated and vaccinated adults in five districts of Bangladesh and thus, investigate the association of seroprevalence and anti-SARS-CoV-2 IgG level with respect to different attributes of study participants. Methods: In the present study, the seroprevalences and levels of plasma anti-SARS-CoV-2 IgG were measured in children (n = 202), unvaccinated adults (n = 112), and vaccinated adults (n = 439) using quantitative ELISA. Results: The overall seroprevalence in the three groups of the study participants were 58.3% (90%CrI: 52.3–64.2%), 62.2% (90%CrI: 54.4–70.0%) and 90.7% (90%CrI: 88.3–92.9%), respectively. Multivariate logistic and linear regression revealed no significant association of seropositivity and levels of anti-SARS-CoV-2 IgG with the baseline characteristics of the children. AB blood group (vs A; aOR=0.21, 95% CI: 0.04–0.92, p = 0.04), O blood group (vs A; aOR=0.09, 95% CI: 0.02–0.32, p = 0.0004), BMI (aOR=1.61, 95% CI: 1.14-2.37, p = 0.01) and overweight obesity status (vs normal, aOR=0.12, 95% CI: 0.02-0.76, p = 0.03) were significantly associated with seropositivity in unvaccinated adults after adjusting for confounders. Age (p = 0.002) was significantly associated with anti-SARS-CoV-2 level in vaccinated adults after adjusting for confounders. Most of the children and unvaccinated adults belonged to the lower antibody response class which implicates the necessity of vaccination. Conclusion: This study portrays a better way of evaluating transmission of virus and gain a better understanding of the true extent of infection as illustrated by the high rates of seroprevalences in children and unvaccinated adults. The findings of this study depicted from the antibody response also suggest the importance of vaccination.

Little is known about the frequency of Zika virus (ZIKV) infections in Sudan. The aim of this study was to obtain data on the prevalence of ZIKV infections and the immunity of the population in the country. To this end, 198 sera obtained between December 2012 and January 2013 in different regions in Sudan were examined for neutralizing antibodies against ZIKV, dengue virus (DENV), and yellow fever virus (YFV). The sera were non-randomly selected. The neutralization titers were compared with each other and with the WHO 1st International Standard for anti-Asian lineage Zika virus antibody. Twenty-six sera neutralized ZIKV. One-third of these sera had higher neutralization titers against ZIKV than against DENV-2 and -3. Two sera showed higher neutralization titers than the WHO standard for ZIKV antibodies. These data suggest occasional ZIKV infections in Sudan. The low percentage of sera in this cohort that neutralized ZIKV indicates that, in the study period, the population was susceptible to ZIKV infection.