The World Health Organization walked back an earlier assertion that transmission of COVID-19 by asymptomatic patients is "very rare."

Dr. Maria Van Kerkhove, head of WHO's emerging diseases and zoonosis unit, made the original comment at a W.H.O. briefing on Monday, said on Tuesday that it was based on just two or three studies and that it was a “misunderstanding” to say asymptomatic transmission is rare globally.

"I was just responding to a question, I wasn't stating a policy of W.H.O. or anything like that," Van Kerkhove said.

"And in that, I used the phrase 'very rare,' and I think that that's misunderstanding to state that asymptomatic transmission globally is very rare. I was referring to a small subset of studies."

An asymptomatic patient is someone with COVID-19 who doesn't have symptoms and never develops symptoms.

Currently, more than 7.1 million COVID-19 infections have been reported globally, with a death toll topping 407,000.