Among those infected with SARS-CoV-2, only a minority will be asymptomatic, Swiss research reports in PLOS Medicine.

The systematic review included nearly 80 studies of people with positive PCR tests for COVID-19 who were followed and monitored for symptoms.

The researchers found that just 20% of those infected with the virus never developed symptoms.

“Our systematic review found that a minority of people have truly asymptomatic SARS-CoV-2 infection and, if they are less infectious than people with symptoms, they probably account for a relatively small proportion of all SARS-CoV-2 transmission,” said researcher Dr Nicola Low, a professor of epidemiology and public health at the Institute of Social and Preventive Medicine at the University of Bern.