WHO moves to clarify asymptomatic transmission comments

The World Health Organization on Wednesday reiterated that it needs more research to establish the extent of asymptomatic transmission of COVID-19.

Maria Van Kerkhove, technical lead of the WHO's Health Emergencies Program, made headlines on Monday after she said at a media conference that "it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual."

But at a live social media Q&A event on Tuesday, she clarified that "this is a major 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, and to truly understand how many people don't have symptoms, we don't actually have that answered yet," she said.

"We do know that some people who are asymptomatic, or some people who don't have symptoms, can transmit the virus on.

"So what we need to better understand is how many of the people in the population don't have symptoms, and separately how many of those individuals go on to transmit to others."

What she had referred to on Monday, she explained, was a very small number of studies. "So I was responding to a question at the press conference. I wasn't stating a policy of the WHO or anything like that," she said, adding that "this is a major unknown".

WHO Director-General Tedros Adhanom Ghebreyesus said on Wednesday that since early February, the WHO has said that asymptomatic people can transmit COVID-19.

"But that we need more research to establish the extent of asymptomatic transmission. That research is ongoing," he told a virtual news conference from Geneva.

Tedros emphasized that it is a new virus and "we are all learning all the time".

"Communicating complex science in real time about a new virus is not always easy, but we believe it's part of our duty to the world. And we can always do better," he said.

CNN contributed to the reporting.