The World Health Organization (WHO) made waves earlier this week by suggesting that the spread of COVID-19 from patients without any symptoms is “very rare.” The statement seemed to contradict months of warnings from health professionals about asymptomatic transmission of the virus. However, on Tuesday, June 9, the WHO walked back the claim, calling the issue a “really complex question.”
The uncertainty began with a WHO news briefing on Monday, June 8. Speaking from the organization’s Geneva headquarters, Dr. Maria Van Kerhove, head of the WHO’s emerging diseases and zoonosis unit, spoke about the organization’s research into asymptomatic transmission.
“From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual,” Dr. Van Kerkhove said. “It’s very rare.”
The statement quickly gained attention, as it seemed to go against previous warnings from medical experts. An April report from the Centers for Disease Control and Prevention (CDC), for example, described the risk of presymptomatic transmission as a reason for social distancing.
While asymptomatic patients never show any symptoms of the disease, presymptomatic ones simply haven’t started showing them yet. The CDC estimates that 40% of all coronavirus transmissions happen before people feel sick.
Infectious disease expert Dr. Anthony Fauci was among those expressing skepticism, telling Good Morning America that the agency’s statement “was not correct.” Dr. Fauci pointed to evidence that 25% to 45% of those infected don’t show symptoms.
“We know from epidemiological studies they can transmit to someone who is uninfected even when they’re without symptoms,” he said. “So to make a statement to say that’s a rare event was not correct.”
Meanwhile, UCLA epidemiology professor Anne Rimoin described a number of ways that people could spread the virus without symptoms.
“When you speak, sometimes you’ll spit a little bit,” she said, according to CNN. “You’ll rub your nose. You’ll touch your mouth. You’ll rub your eyes. And then you’ll touch other surfaces, and then you will be spreading the virus if you are infected and shedding.”
The WHO Clarifies
With their statement being received with confusion by the public, the WHO has moved to clarify its position. In a statement on Tuesday, Dr. Van Kerkhove said that the issue of asymptomatic transmission is a “really complex question,” to which there isn’t yet a definitive answer.
“I was responding to a question at the press conference. I wasn’t stating a policy of WHO or anything like that,” she said, according to CNBC. “I was just trying to articulate what we know. And in that, I used the phrase ‘very rare,’ and I think that’s misunderstanding to state that asymptomatic transmission globally is very rare. I was referring to a small subset of studies.”
Dr. Mike Ryan, executive director of the WHO’s emergency program, echoed Dr. Van Kerhove’s statement.
“There is much to be answered on this. There is much that is unknown,” he said. “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.”