CovidRiskCalc: An online app to calculate the risk of COVID infection in a gathering

ABSTRACT CovidRiskCalc is an evidence based online app which calculates the risk of COVID-19 infection for a person coming into contact during a specific event/gathering with a group of individuals, some of whom may be infected (available at CovidRiskCalc.eu ). The user is helped in providing a rough estimate of the COVID-19 prevalence rate in the group. She also inputs the size of the group, the number (and duration) of her contacts and the level of precautions (masks, social distancing, etc.). The app calculates the user’s risk of transmission in a single infected contact; her probability of infection during the entire event and the number of new infections within the group. Two numerical examples are given. The tool, designed for both professionals and the general public, thus quantifies the risks of infection in special populations (social gatherings, prisons, etc.), but also in general ones (stores, stadiums, etc.).