ABSTRACT
BackgroundThe beginning of the COVID-19 pandemic was shaped by superspreading events including large-scale outbreaks. In Germany the first SARS-CoV-2 outbreak was a superspreading event in a rural area during indoor carnival festivities in February 2020. Methods51 days after the event all known participants were asked to give blood samples, pharyngeal swabs and answer a self-administered questionnaire. Metric room coordinates for all tables, seats, and ventilation-points were assessed. FindingsWe analyzed infection rates among all 411 participants, and the risk of infection in relation to various factors including age, alcohol consumption, and ventilation system. Overall, 46% (n=186/404) of the participants had been infected. We demonstrate that the spatial distribution of infected participants was associated with proximity to the ventilation system (represented as inverse distance, with Odds Ratio OR 1.39, 95% KI [0.86; 2.25]). Interestingly, the risk of infection was highly associated with age, whereby children (OR: 0.33 [0.267; 0.414]) and young adults (age 18-25) had a lower risk of infection than older participants resulting in an average infection risk increase of 28% per 10 years age difference. Behavioral differences also impacted the risk of infection including time spent outside (OR: 0.55 [0.33; 0.91]) or smoking (OR: 0.32 [0.124; 0.81]). InterpretationOur findings underline the importance of proper indoor ventilation for events in the future. The lower susceptibility for children and young adults indicates their limited involvement in superspreading events. FundingThe government of North Rhine-Westphalia (Germany) supported the study with 65,000 Euro. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSThe scientific literature was searched for the term "superspreading event AND Covid-19 OR Sars Cov 2" and identified published papers from China, South Korea, Europe, and North America. Most researchers analyzed superspreading events within a health care setting e.g. in hospitals or nursing homes, or described the general impact of superspreading events on the global pandemic. Only a few metanalyses of transmission clusters analyzed party occasions (e.g. a nightclub in Berlin, Germany) as superspreading events. These reports describe less than 100 infections and are very limited due to missing data or reporting biases. Therefore, the ability to draw scientific conclusions is also limited. Additionally, to our knowledge, there are no studies, which investigated individual behavior, the location, and role of children during a superspreading event. The research for the study started April 2020 and was concluded in June 2021. Added value of this studyOur report analyzes the first COVID-19 superspreading event in Germany in detail, which was not only a unique setting but also included children and adults in the same room. We demonstrate that nearly half of the participants were infected with SARS-CoV-2 and that the proximity of the seating to the ventilation system was an important risk factor for infection. The data showed that low physical distance including singing and duration of attendance at this event increased the risk of infection, while regular smoking and spending the break of the event outside lowered the risk of infection. This underlines the benefit of airing to lower the amount of both droplets and aerosols. Furthermore, we found lower infection in children than adults despite being in the same room suggesting differences in infectability in children. Indeed, we observed that an additional 10 years of age is on average associated with 28% increased risk of infection. Implications of all the available evidenceTaken together, the results demonstrate the importance of the ventilation system during superspreading events. In particular children and young adults had a lower risk of infection during the event indicating that they have a limited role during this pandemic. Overall, our data demonstrate in detail age-dependent infectability as well as highlights to understand transmission dynamics in order to improve comprehensive public health preparedness measures.
Subject(s)
COVID-19 , InfectionsABSTRACT
The world faces an unprecedented SARS-CoV2 pandemic where many critical factors still remain unknown. The case fatality rates (CFR) reported in the context of the SARS-CoV-2 pandemic substantially differ between countries. For SARS-CoV-2 infection with its broad clinical spectrum from asymptomatic to severe disease courses, the infection fatality rate (IFR) is the more reliable parameter to predict the consequences of the pandemic. Here we combined virus RT-PCR testing and assessment for SARS-CoV2 antibodies to determine the total number of individuals with SARS-CoV-2 infections in a given population. Methods: A sero-epidemiological GCP- and GEP-compliant study was performed in a small German town which was exposed to a super-spreading event (carnival festivities) followed by strict social distancing measures causing a transient wave of infections. Questionnaire-based information and biomaterials were collected from a random, household-based study population within a seven-day period, six weeks after the outbreak. The number of present and past infections was determined by integrating results from anti-SARS-CoV-2 IgG analyses in blood, PCR testing for viral RNA in pharyngeal swabs and reported previous positive PCR tests. Results: Of the 919 individuals with evaluable infection status (out of 1,007; 405 households) 15.5% (95% CI: [12.3%; 19.0%]) were infected. This is 5-fold higher than the number of officially reported cases for this community (3.1%). Infection was associated with characteristic symptoms such as loss of smell and taste. 22.2% of all infected individuals were asymptomatic. With the seven SARS-CoV-2-associated reported deaths the estimated IFR was 0.36% [0.29%; 0.45%]. Age and sex were not found to be associated with the infection rate. Participation in carnival festivities increased both the infection rate (21.3% vs. 9.5%, p<0.001) and the number of symptoms in the infected (estimated relative mean increase 1.6, p=0.007). The risk of a person being infected was not found to be associated with the number of study participants in the household this person lived in. The secondary infection risk for study participants living in the same household increased from 15.5% to 43.6%, to 35.5% and to 18.3% for households with two, three or four people respectively (p<0.001). Conclusions: While the number of infections in this high prevalence community is not representative for other parts of the world, the IFR calculated on the basis of the infection rate in this community can be utilized to estimate the percentage of infected based on the number of reported fatalities in other places with similar population characteristics. Whether the specific circumstances of a super-spreading event not only have an impact on the infection rate and number of symptoms but also on the IFR requires further investigation. The unexpectedly low secondary infection risk among persons living in the same household has important implications for measures installed to contain the SARS-CoV-2 virus pandemic.