Forty per cent of people with confirmed Covid-19 infections are asymptomatic, according to a meta-analysis of 95 studies encompassing about 29.8 million people. 

Among all people tested for SARS-CoV-1 (before the emergence of the omicron variant), 0.25 per cent were positive and asymptomatic. The risks of asymptomatic infections were highest among nursing home residents or staff (4.52 per cent), pregnant women (2.34 per cent) and air or cruise passengers (2.02 per cent) 

Based on 77 studies, among the 19,884 people with confirmed SARS-CoV-1, 40.50 per cent were asymptomatic. The risks of asymptomatic infections were highest among nursing home residents or staff (47.53 per cent), pregnant women (54.11 per cent) and air or cruise passengers (52.91 per cent).  

“The high percentage of asymptomatic infections highlights the potential transmission risk of asymptomatic infections in communities,” the authors conclude.

“Screening for asymptomatic infection is required, especially for countries and regions that have successfully controlled SARS-CoV-2. Asymptomatic infections should be under management similar to that for confirmed infections, including isolating and contact tracing.”