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Background Vaccination is the primary strategy to reduce influenza burden. Influenza vaccine effectiveness (VE) can vary annually depending on circulating strains. Methods We used a test-negative case-control study design to estimate influenza VE against laboratory-confirmed influenza-related hospitalizations among children (aged 6 months–17 years) across 5 influenza seasons in Atlanta, Georgia, from 2012–2013 to 2016–2017. Influenza-positive cases were randomly matched to test-negative controls based on age and influenza season in a 1:1 ratio. We used logistic regression models to compare odds ratios (ORs) of vaccination in cases to controls. We calculated VE as [100% × (1 – adjusted OR)] and computed 95% confidence intervals (CIs) around the estimates. Results We identified 14 596 hospitalizations of children who were tested for influenza using the multiplex respiratory molecular panel; influenza infection was detected in 1017 (7.0%). After exclusions, we included 512 influenza-positive cases and 512 influenza-negative controls. The median age was 5.9 years (interquartile range, 2.7–10.3), 497 (48.5%) were female, 567 (55.4%) were non-Hispanic Black, and 654 (63.9%) children were unvaccinated. Influenza A accounted for 370 (72.3%) of 512 cases and predominated during all 5 seasons. The adjusted VE against influenza-related hospitalizations during 2012–2013 to 2016–2017 was 51.3% (95% CI, 34.8% to 63.6%) and varied by season. Influenza VE was 54.7% (95% CI, 37.4% to 67.3%) for influenza A and 37.1% (95% CI, 2.3% to 59.5%) for influenza B. Conclusions Influenza vaccination decreased the risk of influenza-related pediatric hospitalizations by >50% across 5 influenza seasons. [ABSTRACT FROM AUTHOR]

The serial interval and effective reproduction number for coronavirus disease (COVID-19) are heterogenous, varying by demographic characteristics, region, and period. During February 1-July 13, 2020, we identified 4,080 transmission pairs in Georgia, USA, by using contact tracing information from COVID-19 cases reported to the Georgia Department of Public Health. We examined how various transmission characteristics were affected by symptoms, demographics, and period (during shelter-in-place and after subsequent reopening) and estimated the time course of reproduction numbers for all 159 Georgia counties. Transmission varied by time and place but also by persons' sex and race. The mean serial interval decreased from 5.97 days in February-April to 4.40 days in June-July. Younger adults (20-50 years of age) were involved in most transmission events occurring during or after reopening. The shelter-in-place period was not long enough to prevent sustained virus transmission in densely populated urban areas connected by major transportation links. [ABSTRACT FROM AUTHOR]

Linguistically speaking, the predominant viral cause of gastroenteritis has been evolving. Once evocatively called winter vomiting disease, the pathogen's name has changed alongside improved scientific understanding. First called Norwalk virus [...]

Abstract Background Reverse transcription-polymerase chain reaction (RT-PCR) is the main method for laboratory diagnosis of norovirus-associated infectious intestinal disease (IID). However, up to 16% of healthy individuals in the community, with no recent history of IID, may be RT-PCR positive; so it is unclear whether norovirus is actually the cause of illness in an IID case when they are RT-PCR positive. It is important to identify the pathogen causing illness in sporadic IID cases, for clinical management and for community based incidence studies. The aim of this study was to investigate how faecal viral load can be used to determine when norovirus is the most likely cause of illness in an IID case. Methods Real-time RT-PCR was used to determine the viral load in faecal specimens collected from 589 IID cases and 159 healthy controls, who were infected with genogroup II noroviruses. Cycle threshold (Ct) values from the real-time RT-PCR were used as a proxy measure of viral load. Receiver-operating characteristic (ROC) analysis was used to identify a cut-off in viral load for attributing illness to norovirus in IID cases. Results One hundred and sixty-nine IID cases and 159 controls met the inclusion criteria for the ROC analysis. The optimal Ct value cut-off for attributing IID to norovirus was 31. The same cut-off was selected when using healthy controls, or IID cases who were positive by culture for bacterial pathogens, as the reference negative group. This alternative reference negative group can be identified amongst specimens routinely received in clinical virology laboratories. Conclusion We demonstrated that ROC analysis can be used to select a cut-off for a norovirus real time RT-PCR assay, to aid clinical interpretation and diagnose when norovirus is the cause of IID. Specimens routinely received for diagnosis in clinical virology laboratories can be used to select an appropriate cut-off. Individual laboratories can use this method to define in-house cut-offs for their assays, to provide the best possible diagnostic service to clinicians and public health workers. Other clinical and epidemiological information should also be considered for patients with Ct values close to the cut-off, for the most accurate diagnosis of IID aetiology.

Abstract Background Noroviruses are highly infectious pathogens that cause gastroenteritis in the community and in semi-closed institutions such as hospitals. During outbreaks, multiple units within a hospital are often affected, and a major question for control programs is: are the affected units part of the same outbreak or are they unrelated transmission events? In practice, investigators often assume a transmission link based on epidemiological observations, rather than a systematic approach to tracing transmission. Here, we present a combined molecular and statistical method for assessing: 1) whether observed clusters provide evidence of local transmission and 2) the probability that anecdotally|linked outbreaks truly shared a transmission event. Methods 76 healthcare associated outbreaks were observed in an active and prospective surveillance scheme of 15 hospitals in the county of Avon, England from April 2002 to March 2003. Viral RNA from 64 out of 76 specimens from distinct outbreaks was amplified by reverse transcription-PCR and was sequenced in the polymerase (ORF 1) and capsid (ORF 2) regions. The genetic diversity, at the nucleotide level, was analysed in relation to the epidemiological patterns. Results Two out of four genetic and epidemiological clusters of outbreaks were unlikely to have occurred by chance alone, thus suggesting local transmission. There was anecdotal epidemiological evidence of a transmission link among 5 outbreaks pairs. By combining this epidemiological observation with viral sequence data, the evidence of a link remained convincing in 3 of these pairs. These results are sensitive to prior beliefs of the strength of epidemiological evidence especially when the outbreak strains are common in the background population. Conclusion The evidence suggests that transmission between hospitals units does occur. Using the proposed criteria, certain hypothesized transmission links between outbreaks were supported while others were refuted. The combined molecular/epidemiologic approach presented here could be applied to other viral populations and potentially to other pathogens for a more thorough view of transmission.

Abstract Emerging Themes in Epidemiology is a new, online Open Access journal. This editorial – which coincides with the Journal's launch – describes its unique review and publication model. The editorial board and review process of ETE will be managed by research degree students and will therefore be a training ground for students (though final editorial control rests with senior faculty Associate Editors). With our mix of Open Access publishing and the strong involvement of students in editing and reviewing, we believe that Emerging Themes in Epidemiology will be a progressive medium for promoting new ideas in epidemiology.

Abstract In this first special theme issue, Emerging Themes in Epidemiology publishes a collection of articles on the theme of Epidemiology in conflict. Violent conflict is an issue of great sensitivity within public health, but more structured research and reasoned discussion will allow us to better mitigate the public health impacts of war, and place the public health community in a more informed position in discussions about possible interventions in future conflicts.

Abstract Background Noroviruses are the most common cause of gastroenteritis outbreaks in industrialised countries. Gastroenteritis caused by Norovirus infection has been described as a highly seasonal syndrome, often referred to as "winter vomiting disease". Methods The Public Health Laboratory Service Communicable Disease Surveillance Centre has systematically collected reports of laboratory confirmed cases of Norovirus-gastroenteritis since 1995. We analysed these data for annual and seasonal trends and age distribution. Results A mid-summer peak in reported cases of Norovirus was observed in 2002, unlike all six previous years when there was a marked summer decline. Total reports from 2002 have also been higher than all previous years. From the first 10 months of 2002, a total of 3029 Norovirus diagnoses were reported compared the previous peak in 1996 of 2437 diagnoses for the whole 12-month period. The increase in 2002 was most marked in the 65 and older age group. Conclusion This surveillance data challenges the view that Noroviruses infections exclusively have wintertime seasonality.

Background Large norovirus (NoV) outbreaks are explosive in nature and vary widely in final size and duration, suggesting that superspreading combined with heterogeneous contact may explain these dynamics. Modeling tools that can capture heterogeneity in infectiousness and contact are important for NoV outbreak prevention and control, yet they remain limited. Methods Data from a large NoV outbreak at a Dutch scout jamboree, which resulted in illness among 326 (of 4500 total) individuals from 7 separate camps, were used to examine the contributions of individual variation in infectiousness and clustered contact patterns to the transmission dynamics. A Bayesian hierarchical model of heterogeneous, clustered outbreak transmission was applied to represent (1) between-individual heterogeneity in infectiousness and (2) heterogeneous patterns of contact. Results We found wide heterogeneity in infectiousness across individuals, suggestive of superspreading. Nearly 50% of individual infectiousness was concentrated in the individual's subcamp of residence, with the remainder distributed over other subcamps. This suggests a source-and-sink dynamic in which subcamps with greater average infectiousness fed cases to those with a lower transmission rate. Although the per capita transmission rate within camps was significantly greater than that between camps, the large pool of susceptible individuals across camps enabled similar numbers of secondary cases generated between versus within camps. Conclusions The consideration of clustered transmission and heterogeneous infectiousness is important for understanding NoV transmission dynamics. Models including these mechanisms may be useful for providing early warning and guiding outbreak response. [ABSTRACT FROM AUTHOR]

Background: In 2006, Brazil began routine immunization of infants Methods and Findings: National data were analyzed with an interrupted time-series analysis that used diarrhea-related mortality or hospitalization rates as the main outcomes. Monthly mortality and admission rates estimated for the years after rotavirus vaccination (2007-2009) were compared with expected rates calculated from pre-vaccine years (2002-2005), adjusting for secular and seasonal trends. During the three years following rotavirus vaccination in Brazil, rates for diarrhea-related mortality and admissions among children Conclusions: After the introduction of rotavirus vaccination for infants, significant declines for three full years were observed in under-5-y diarrhea-related mortality and hospital admissions for diarrhea in Brazil. The largest reductions in diarrhea-related mortality and hospital admissions for diarrhea were among children younger than 2 y, who were eligible for vaccination as infants, which suggests that the reduced diarrhea burden in this age group was associated with introduction of the rotavirus vaccine. These real-world data are consistent with evidence obtained from clinical trials and strengthen the evidence base for the introduction of rotavirus vaccination as an effective measure for controlling severe and fatal childhood diarrhea. Please see later in the article for the Editors' Summary., Introduction In July 2009, the World Health Organization recommended introduction of rotavirus vaccines into national immunization programs of all countries worldwide for controlling severe rotavirus disease, which accounts for approximately [...]

Norovirus is the leading cause of acute gastroenteritis and foodborne disease in the United States. The Food and Drug Administration recommends that food workers infected with norovirus be excluded from the workplace while symptomatic and for 48 hours after their symptoms subside. Compliance with this recommendation is not ideal, and the population-level impacts of changes in food-worker compliance have yet to be quantified. We aimed to assess the population impacts of varying degrees of compliance with the current recommendation through the use of a compartmental model. We modeled the number and proportion of symptomatic norovirus cases averted annually in the US population (using data from 1983–2014) in specific age groups (children aged <5 years, children aged 5–17 years, adults aged 18–64 years, and adults aged ≥65 years) under various scenarios of food-worker exclusion (i.e. proportion compliant and days of postsymptomatic exclusion) in comparison with a referent scenario which assumed that 66. 6 ¯ % of norovirus-symptomatic food workers and 0% of postsymptomatic food workers were excluded from work. Overall, we estimated that 6.0 million cases of norovirus have already been avoided annually under the referent scenario and that 6.7 million (28%) more cases might be avoided through 100% compliance with the current recommendations. Substantial population-level benefits were predicted from improved compliance in exclusion of norovirus-infected food workers from the workplace—benefits that may be realized through policies or programs incentivizing self-exclusion. [ABSTRACT FROM AUTHOR]

We compared acute gastroenteritis (AGE)-related hospitalization rates among children <5 years of age during the pre–rotavirus vaccine (2000–2006) and post–rotavirus vaccine (2008–2013) periods to estimate national reductions in AGE-related hospitalizations and associated costs. We estimate that between 2008 and 2013, AGE-related hospitalizations declined by 382000, and $1.228 billion in medical costs were averted. [ABSTRACT FROM AUTHOR]