Asymptomatic transmission of coronavirus may be worse than SARS or influenza

Asymptomatic transmission ‘is the Achilles’ heel of COVID-19 pandemic control through the public-health strategies we have currently deployed,’ one study says

How worried should you be about asymptomatic transmission of COVID-19?

The World Health Organization on Tuesday attempted to clarify comments made just 24 hours earlier that transmission of the novel coronavirus in carriers who don’t show apparent symptoms happened in “very rare” cases.

Dr. Maria Van Kerkhove said it was a “misunderstanding to state that asymptomatic transmission globally is very rare,” and that her comments during Monday’s WHO news briefing had been based on “a very small subset of studies.” “I was just responding to a question; I wasn’t stating a policy of WHO,” she said.

The WHO currently estimates that 16% of people with COVID-19 are asymptomatic and can transmit the coronavirus, while other data show that 40% of coronavirus transmission is due to carriers not displaying symptoms of the illness.

Public-health officials have advised people to keep a distance of six feet from one another. Face masks are designed to prevent the wearer, who may be infected with COVID-19 but have very mild or no symptoms, from spreading invisible droplets to another person and thereby infecting them too.

But “there’s nothing magic about six feet,” said Gregory Poland, who studies the immunogenetics of vaccine response in adults and children at the Mayo Clinic in Rochester, Minn., and is an expert with the Infectious Diseases Society of America.

“The virus can’t measure,” he told MarketWatch. “For example, the viral cloud while speaking will extend 27 feet and linger in the air for about 30 minutes. This is more like influenza in the sense that people transmit the virus prior to experiencing any symptoms and some people, of course, will not get sick.”

Also see: Yes, America needs to brace itself for a second wave of coronavirus

Asymptomatic transmission “is the Achilles’ heel of COVID-19 pandemic control through the public-health strategies we have currently deployed,” according to a study by researchers at the University of California, San Francisco published May 28 in the New England Journal of Medicine.

“Symptom-based screening has utility, but epidemiologic evaluations of COVID-19 outbreaks within skilled nursing facilities ... strongly demonstrate that our current approaches are inadequate,” researchers Monica Gandhi, Deborah Yokoe and Diane Havlir wrote.

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