Forty percent of people with coronavirus infections have no symptoms. Might they be the key to ending the pandemic?

Cycling fans wearing protective face masks watch the riders arriving prior to the start of the one-day Milan-San Remo classic cycling race in Milan on Aug. 8. (Marco Bertorello/AFP/Getty Images)

New research suggests that some of us may be partially protected due to past encounters with common cold coronaviruses

When researcher Monica Gandhi began digging deeper into outbreaks of the novel coronavirus, she was struck by the extraordinarily high number of infected people who had no symptoms.

A Boston homeless shelter had 147 infected residents, but 88 percent had no symptoms even though they shared their living space. A Tyson Foods poultry plant in Springdale, Ark., had 481 infections, and 95 percent were asymptomatic. Prisons in Arkansas, North Carolina, Ohio and Virginia counted 3,277 infected people, but 96 percent were asymptomatic.

During its seven-month global rampage, the coronavirus has claimed more than 700,000 lives. But Gandhi began to think the bigger mystery might be why it has left so many more practically unscathed.

What was it about these asymptomatic people, who lived or worked so closely to others who fell severely ill, she wondered, that protected them? Did the “dose” of their viral exposure make a difference? Was it genetics? Or might some people already have partial resistance to the virus, contrary to our initial understanding?

Efforts to understand the diversity in the illness are finally beginning to yield results, raising hope the knowledge will help accelerate development of vaccines and therapies — or possibly even create new pathways toward herd immunity in which enough of the population develops a mild version of the virus that they block further spread and the pandemic ends.

“A high rate of asymptomatic infection is a good thing,” said Gandhi, an infectious-disease specialist at the University of California at San Francisco. “It’s a good thing for the individual and a good thing for society.”

The coronavirus has left numerous clues — the uneven transmission in different parts of the world, the mostly mild impact on children. Perhaps most tantalizing is the unusually large proportion of infected people with no symptoms. The Centers for Disease Control and Prevention last month estimated that rate at about 40 percent.

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Source: Ariana Eunjung Cha | The Washington Post