“Keep in mind that a person with either asymptomatic or pre-symptomatic SARS-CoV-2 infection can still transmit the virus,” the study’s co-authors Diana Buitrago-Garcia and Nicola Low said in a statement.
The researchers from the University of Bern in Switzerland analyzed seventy-nine studies containing data on more than 6,000 individuals—with about 1,300 defined as asymptomatic—to determine the proportion of people with an infection who never developed the associated coronavirus symptoms.
According to Dr. Susan Kline, a professor of infectious diseases with the University of Minnesota in Minneapolis, the new figure of 20% is on the low end of what was anticipated.
“I thought it was somewhere between about 15 percent and 50 percent,” she told HealthDay.
“I think this is a nice paper because it has pulled in a lot of different articles and then they show how all their estimates vary and they point out some of the differences in the way the studies were set up. … I would say 20 percent is still a fairly large number.”
Some medical experts say that people may actually have symptoms but not realize they are direct signs of the novel coronavirus.
“There is some indication that many asymptomatic people actually suffer occult (hidden) disease, which affects their actual physical abilities during the infection and for some time thereafter,” Dr. William Haseltine, a former professor at Harvard Medical School and Harvard School of Public Health and the founder and chair of the division of biochemical pharmacology and the division of human retrovirology, told Healthline.
The study’s findings seem to support the need for further public-health measures that have proven to be effective in limiting the spread of the virus.
“Masks, social distancing, hand-washing, and avoiding crowds—we know these are the four things that really will mitigate the spread,” Dr. Len Horovitz, a pulmonary specialist with Lenox Hill Hospital in New York City, told HealthDay.
Just last week, the U.S. Centers for Disease Control and Prevention released guidance saying that even people who don’t show symptoms of the coronavirus should be tested if they’ve been exposed to the novel coronavirus.
Now more than eight months into the pandemic, there are roughly 31.7 million confirmed cases of coronavirus worldwide, including at least 973,000 related deaths, according to the latest data from Johns Hopkins University.
Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek and Arirang TV. Follow or contact him on LinkedIn.