The WHO health expert who made the comment yesterday said that it was a "misunderstanding" of research on the topic

By Julie Mazziotta and Eric Todisco
June 09, 2020 01:42 PM

The World Health Organization is pulling back a claim that asymptomatic spread of the new coronavirus, COVID-19, from people who never show symptoms, is "very rare," after criticism from health experts.

On Monday, Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, said at a news briefing from the United Nations agency’s Geneva headquarters that, “from the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual. It's very rare."

Her claim went against the thinking of most health experts and the Centers for Disease Control, which started urging Americans to wear masks due to the high risk of asymptomatic spread.

On Tuesday, Van Kerkhove pulled back that claim during a special news conference, saying that it was a "misunderstanding" and that it is still not known how much asymptomatic spread contributes to COVID-19 cases.

Van Kerkhove said that she was trying to answer a journalist's question when she made the "very rare" claim, and that she "wasn’t stating a policy of WHO or anything like that,” she said.

“We do know that some people who are asymptomatic, or some people who do not have symptoms, can transmit the virus on," she added.

Credit: Spencer Platt/Getty Images

Van Kerkhove's comments were based on a new WHO report on COVID-19 spread, in which they advised that the general public wear masks to reduce the chance of transmission. The agency analzyed studies on COVID-19 transmission for the report, and found that people are more likely to spread COVID-19 if they are pre-symptomatic — meaning they have the virus but have not yet started showing symptoms and are likely unaware, and therefore less cautious about going out in public.

However, WHO writes in the report that "most studies included in this review have important limitations of poor reporting of symptoms, or did not properly define which symptoms they were investigating."

While recounting her previous statements on Tuesday, Van Kerkhove said that the studies on transmission may use flawed data.

“That’s a big open question, and that remains an open question,” she said.

People walk at the boardwalk in Venice Beach over Memorial Day Weekend
| Credit: APU GOMES/AFP via Getty Images

On Monday, health experts refuted the idea that asymptomatic cases are only causing a limited amount of spread.

“All of the best evidence suggests that people without symptoms can and do readily spread SARS-CoV-2, the virus that causes COVID-19,” scientists at the Harvard Global Health Institute said in a statement on Tuesday.

“The bottom line is this: there are people out there without symptoms who are shedding virus and spreading the disease," Dr. Ashish Jha, faculty director of the Harvard Global Health Institute, said on Morning Joe Tuesday morning.

And many experts, including WHO and Van Kerkhove, emphasized that social distancing, COVID-19 testing and tracing, masks-wearing and quarantining is essential to reducing the spread.

Also on Monday, WHO announced that the number of new COVID-19 cases worldwide had hit a high, with 136,000 new infections on Sunday. The majority of the cases — three-quarters — are in just 10 countries, primarily in the Americas and South Asia, as the number of new cases in Europe continues to drop following their strict lockdowns.

Although the U.S. is continuing to lift its stay-at-home restrictions, at least 20 states have seen a recent spike in coronavirus cases, particularly Florida, Arkansas, Mississippi and the Carolinas. As of Tuesday, more than 1,970,600 Americans have been diagnosed with COVID-19, and at least 110,960 people have died.