WHO: Patients most infectious when they first show symptoms

A shopper browses second-hand clothing for sale at Yaba market, amid the coronavirus disease (COVID-19) outbreak, in Lagos, Nigeria

Studies show people with the coronavirus are most infectious when they first show symptoms, Maria van Kerkhove, an epidemiologist and the World Health Organization’s technical lead on the pandemic, said in a briefing on Tuesday.

She said a sub-set of people do not develop symptoms, but can still infect others, and as many as 40% of transmissions may be by asymptomatic cases.