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Officials at the World Health Organization walked back comments made Monday that the spread of the novel coronavirus by people who are not displaying symptoms is “very rare.”

Dr. Maria Van Kerkhove said Tuesday that there had been “misunderstandings” about what she announced on Monday.

“In that I used the phrase ‘very rare,’ and I think that’s misunderstanding to state that asymptomatic transmission globally is very rare,” she said. “What I was referring to is a subset of studies.”

Van Kerkhove said that asymptomatic people — meaning people who have the virus but do not display symptoms — can, in fact, spread the virus, though she said no one knows how common it is.

“We do know that some people who are asymptomatic or some people who don’t have symptoms can transmit the virus on,” she said.

The announcement that transmission by carriers without symptoms is “very rare,” drew immediate pushback from health experts who have said for months that the virus can be spread by infected people even if they do not display symptoms.

Citing data collected from around the world, Van Kerkhove, WHO’s technical lead on COVID-19, said at the press briefing on Monday that spread by asymptomatic and presymptomatic people does occur, but since the instances are so rare, WHO recommends focusing on tracing and isolating symptomatic people to stop the spread of the virus.

Asymptomatic people are those who have the virus but never show symptoms of the disease, while presymptomatic means a person has been infected but has not yet shown symptoms of the virus.

The WHO announcement caused confusion because many health experts have said that people should wear masks and practice social distancing because those infected with the COVID-19 virus who are asymptomatic are able to spread the virus to others.

“Some modeling studies suggest 40-60% of spread is from people when they didn’t have symptoms,” tweeted Ashish Jha, incoming dean at the Brown School of Public Health, in response to the WHO announcement.

In April, the Centers for Disease Control and Prevention began recommending that people wear some sort of face coverings when out in public because studies have indicated that people without symptoms are able to spread the virus.

The WHO has maintained that asymptomatic spread is not a driver of the pandemic and probably accounts for about 6% of spread, at most.

Van Kerkhove said she was relying on “two or three studies” as well as unpublished reports from some countries for the statement she made on Monday. She said perhaps “very rare” is not the best phrase to use.