Most people infected with SARS-CoV-2 develop symptoms

While some people who contract SARS-CoV-2 infections never experience any symptoms, there remains disagreement about what proportion of total infections these cases comprise. A study by researchers of the Institute of Social and Preventive Medicine of the University of Bern suggests that true asymptomatic cases of SARS-CoV-2 comprise a minority of infections. The full spectrum and distribution of the severity of COVID-19 symptoms are not well understood. Some infected people may experience severe infections resulting in viral pneumonia, respiratory distress syndrome, and death, while others remain completely asymptomatic or develop mild, nonspecific symptoms. To better understand the proportion of people who become infected with SARS-CoV-2 and never develop any symptoms, as well as the proportion of people who are asymptomatic at the time of diagnosis, but develop symptoms later, researchers of the Institute of Social and Preventive Medicine (ISPM) of the University of Bern systematically reviewed literature using a database of SARS-CoV-2 evidence between January and June 2020. The researchers then analysed 79 studies reporting empirical data on about 6,616 people, 1,287 of whom were defined as asymptomatic in order to determine the proportion of infected people who never developed symptoms. The new study in PLOS Medicine estimated that about 20% of COVID-19 infections remained asymptomatic during follow up, based on all 79 studies.