Asymptomatic covid-19 cases aren't infectious - WHO

The spread of Covid-19 by someone who is not showing symptoms appears to be rare, Maria Van Kerkhove, the World Health Organization's technical lead for coronavirus response and head of the emerging diseases and zoonoses unit, said during a media briefing in Geneva on Monday.

A top World Health Organization official clarified on Tuesday last week that scientists have not determined yet how frequently people with asymptomatic cases of Covid-19 pass the disease on to others, a day after suggesting that such spread is “very rare.”

The clarification comes after the WHO’s original comments incited strong pushback from outside public health experts, who suggested the agency had erred, or at least miscommunicated, when it said people who didn’t show symptoms were unlikely to spread the virus. 

From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual, Van Kerkhove said on Monday.

We have a number of reports from countries who are doing very detailed contact tracing. They're following asymptomatic cases, they're following contacts and they're not finding secondary transmission onward. It is very rare -- and much of that is not published in the literature, she said.

We are constantly looking at this data and we're trying to get more information from countries to truly answer this question. It still appears to be rare that an asymptomatic individual actually transmits onward.