Analysis of the Dynamics, Outcome, and Prerequisites of the first German SARS-CoV-2 Superspreading Event

Wessendorf, L.; Richter, E.; Schulte, B.; Schmithausen, R. M.; Exner, M.; Lehmann, N.; Coenen, M.; Fuhrmann, C.; Kellings, A.; Huesing, A.; Joeckel, K.-H.; Streeck, H.

Background The 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. Methods 51 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. Findings We 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]). Interpretation Our 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.