WHO scrambles to clarify comments on asymptomatic coronavirus spread, says much is still unknown

The World Health Organization scrambled Tuesday to clarify its comments earlier this week that transmission of the coronavirus by people who never developed symptoms is "very rare," which drew skepticism from physicians and others across social media. 

Dr. Maria Van Kerkhove, head of WHO's emerging diseases and zoonosis unit, said it's a "really complex question" and much is still unknown.

"The majority of transmission that we know about is that people who have symptoms transmit the virus to other people through infectious droplets. But there are a subset of people who don't develop symptoms," she said on a live Q&A streamed across multiple social media platforms. "To truly understand how many people don't have symptoms, we don't actually have that answer yet." 

Asymptomatic spread of the coronavirus does occur, Dr. Mike Ryan, executive director of the WHO's emergencies program, said during the Q&A. However, the portion of asymptomatic individuals who transmit the virus remains a "big open question."

"There is much to be answered on this. There is much that is unknown," he added. "It's clear that both symptomatic and asymptomatic individuals are part of the transmission cycle. The question is what is the relative contribution of each group to overall number of cases."

An asymptomatic person is someone with Covid-19 who doesn't have symptoms and never develops symptoms. It's not the same as someone who later develops symptoms, who would be classified as pre-symptomatic, WHO officials said.

On Monday, WHO officials said asymptomatic people aren't driving the spread of the virus, casting doubt on concerns by some researchers that the disease could be difficult to contain due to asymptomatic infections.

"From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual," Kerkhove said at a news briefing Monday from the WHO's Geneva headquarters. "It's very rare."

Kerkhove said Tuesday she was referring to "a very few studies, some two or three studies, that have been published that actually tried to follow asymptomatic cases."

"That's a very small subset of studies," she said.

This is a developing story. Please check back for updates.

Source: cnbc.com