Immune To COVID? New Study Suggests Why

A World Health Organization official on Tuesday attempted to clarify her statement that the chances of an asymptomatic person passing along the coronavirus infection is "very rare."

Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, said Monday during a media briefing, "It still appears to be rare that an asymptomatic individual actually transmits onward to a secondary individual."

However, the announcement was immediately met with skepticism and pushback from prominent health and medical experts.

During a Q&A Tuesday, Van Kerkhove clarified that transmission by asymptomatic people "is a major unknown," according to a report from CNN.

"We do know that some people who are asymptomatic or some people who do not have symptoms can transmit the virus on — so what we need to better understand is how many people in the population don’t have symptoms," Van Kerkhove said.

She explained further:

"What I was referring to yesterday in the press conference were very few studies who tried to look at asymptomatic cases over time. … And that’s a very small subset of studies, and so I was responding to a question at the press conference. I wasn’t stating a policy," Van Kerkhove said. "Because this is a major unknown, because there are so many unknowns around this, some modeling groups had tried to estimate what is the proportion of asymptomatic people who may transmit."

Mike Ryan, executive director of the WHO Health Emergencies Program, also said during the Q&A that there is still much to learn about the possible asymptomatic spread of the coronavirus.

"Whatever proportion of disease is transmitting from asymptomatic individuals, as Maria said, that is unknown," Ryan said. "There’s much to be answered about this, there’s much unknown."

Early in the pandemic, evidence suggested that person-to-person transmission among people who didn't have symptoms could lead to outbreaks. It was one of the assumptions that led to social distancing restrictions and calls for people to use masks.

After Van Kerkhove spoke Monday, experts cautioned to not get caught up whether people are asymptomatic or pre-symptomatic.

People who are infected yet never show symptoms are considered truly asymptomatic cases. Other people who are infected but don't show symptoms until later on would be considered presymptomatic, acccording to The Washington Post. And then some people do have symptoms that are mild or that they don't consider to be from COVID-19, such as diarrhea or muscle aches.

"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.

Eric Topol, a doctor and professor of molecular medicine and founder and director of Scripps Research Translational Institute, said Van Kerkhove's statement created "significant confusion."

He tweeted that a conservative estimate is that 40% to 45% of infected people "don't (ever) develop symptoms." He added that more study needs to be done on how frequently asymptomatic people can transmit the infection.

"For now, it is appropriate to assume anyone (you or others) can be asymptomatic and masks are essential. And physical distancing," Topol said.

Worldwide, the total number of infections has reached more than 7.2 million and over 407,300 people have died. The U.S. has recorded nearly 2 million cases and more than 111,130 deaths.

Latest Developments

United States:

-Yosemite National Park plans to reopen on Thursday to about 50% of its usual June visitors, but most visitors will need a new day use reservation to get into the national park. Day use reservations for June and July go on sale today.

-Workers at a Tesla plant California tested positive last month after Elon Musk reopened the production facility in Fremont in defiance of local shutdown rules, The Washington Post reported. Supervisors met with employees to tell them the company had reported several cases of COVID-19, according to the Post, which cited two workers who spoke anonymously.

Worldwide:

-Spain’s Health Minister Salvador Illa announced face masks will be required in public places until the coronavirus pandemic ends.

-A study that looked at hospital parking lots and online searches of symptoms like “cough” and “diarrhea” suggests the novel coronavirus may have been spreading in Wuhan, China, as early as last fall.

For the latest coronavirus information in your county and a full list of important resources to help you make the smartest decisions regarding the disease, check out our dedicated COVID-19 page.

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