Numerous experts worldwide and the Centers for Disease Control and Prevention have warned that people without coronavirus symptoms could still transmit the virus, which explains why the pandemic has been so hard to contain.
So, it was a surprise when Maria Van Kerkhove, the World Health Organization’s technical lead on COVID-19, seemed to suggest at a press briefing on Monday that the likelihood of contracting the coronavirus from asymptomatic individuals, or those with no clinical symptoms, appeared to be "very rare."
Van Kerkhove clarified on Tuesday during a WHO live stream that there is still a lot they don't know about the virus, saying her original comments tried to "articulate what we know."
She added that it was a "misunderstanding" to state that asymptomatic transmission is "rare."
"What I was referring to yesterday in the press conference was a subset of substudies. I also referred to some data that isn’t published," she said. "These are estimates, and there’s a big range from the different models. Some estimates of around 40 percent of transmission may be due to asymptomatic, but those are from models and so I didn’t include that in my answer yesterday."
She also stressed that there's a big difference with asymptomatic spread, where a person never shows symptoms, and a person being "presymptomatic," where they transmit the virus before developing mild symptoms.
Van Kerkhove added that some estimates suggest "anywhere between 6% of the population and 41% of the population may be infected but not have symptoms within a point estimate of around 16%."
Overall, Van Kerkhove stressed that they know the "majority" of transmission comes from people with coronavirus symptoms, but those who don't have symptoms can still pass the virus on.
She added that it still remains a "big open question" as to what percentage of people who are truly asymptomatic transmit the disease to others.
Van Kerkhove said that based on data, when people without symptoms of COVID-19 are tracked over a period of time, there are very few cases of spread.
“We are constantly looking at this data and we’re trying to get more information from countries to truly answer this question,” she said. “It still appears to be rare that asymptomatic individuals actually transmit onward.”
She added that if we were to isolate all individuals with symptomatic cases, and their contacts, we would "drastically" reduce the transmission of COVID-19.
The head of the World Health Organization warned Monday that the coronavirus pandemic is worsening globally, even as the situation in Europe is improving.
At the press briefing on Monday, Tedros Adhanom Ghebreyesus noted that about 75% of cases reported to the U.N. health agency on Sunday came from 10 countries in the Americas and South Asia. He noted that more than 100,000 cases have been reported on nine of the past 10 days — and that the 136,000 cases reported Sunday was the biggest number so far.
Tedros said most countries in Africa are still seeing an increase in cases, including in new geographic areas even though most countries on the continent have fewer than 1,000 cases.
“At the same time, we’re encouraged that several countries around the world are seeing positive signs,” Tedros said. “In these countries, the biggest threat now is complacency.”