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.
Those clues have sent scientists off in different directions: Some are looking into the role of the receptor cells, which the virus uses to infiltrate the body, to better understand the role that age and genetics might play. Others are delving into face masks and whether they may filter just enough of the virus so that those wearing them had mild cases or no symptoms at all.
The theory that has generated the most excitement in recent weeks is that some people walking among us might already have partial immunity....
