Studies suggest millions of people who have been infected with the coronavirus never even realized they had it, never felt ill, never had any symptoms. That doesn’t mean they didn’t pass it along.
Are asymptomatic people contagious? And if so, how effectively do they spread COVID-19? The debate continues among infectious disease experts on both of those questions, but a new study provides some answers.
Researchers in South Korea tested 303 people in isolation following an outbreak, to determine their viral load, meaning how much of the coronavirus was in their bodily fluid. About 30% of them were asymptomatic, while the rest were already ill or soon would be.
Testing found roughly the same level of coronavirus in the noses, throats and mouths of asymptomatic patients as those who were sick — suggesting they may be just as able to spread COVID-19.
Scientists didn’t track the asymptomatic carriers after testing to see if they infected others, the study said. Still, their findings provide more evidence for asymptomatic spread, which is often cited by experts and officials.
The World Health Organization estimates 16% of people who catch the coronavirus don’t experience symptoms and can infect others, Market Watch reported.
But the WHO also says “the extent of truly asymptomatic infection in the community remains unknown,” according to a scientific brief published in July.
More than half of coronavirus patients don’t know how they caught it, according to the Centers for Disease Control and Prevention. Experts point the finger at asymptomatic carriers.
“We know that most of the spread are from asymptomatic people, particularly young adults,” Adm. Brett Giroir of the Department of Health and Human Services told CNBC in July.
Giroir said the prevalence of asymptomatic spread means much more coronavirus testing is needed.
“Early on, we had a very tight limitation of testing, so we were really dealing with those who were symptomatic in the hospital or health care workers. Now, it’s very, very important that we actually test those who are asymptomatic,” he advocates. “You’ve got to cast a wide net.”
As of Friday, more than 160,000 Americans have died as a result of the coronavirus, and 4.9 million have been infected, according to Johns Hopkins University. Over 19 million cases have been confirmed worldwide, and 716,000 have died.