New estimates of the number of asymptomatic people with the coronavirus suggest that “silent” COVID-19 is much more prevalent than once thought — but these individuals may not spread the virus for as long as symptomatic patients do, a study from China suggests.
The report, based on 78 people in Wuhan, China, was published Wednesday in the journal JAMA Network Open. All of the patients were confirmed to have COVID-19; a little more than half of the patients (58 percent) had symptoms, while 42 percent did not.
The cases were identified through government screening, which requires that all close contacts of confirmed cases also be tested for the virus, the researchers wrote.
The asymptomatic patients were more likely to be women, and more likely to be younger, in their 20s, 30s and early 40s.
And the researchers found the asymptomatic individuals shed the virus for about eight days, compared with 19 days among those who did have symptoms.
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Still, asymptomatic COVID-19 cases remain a concern, researchers at Zhongnan Hospital of Wuhan University wrote, because they may have “unknowingly transmitted the virus to others.”
Even if infected people are not actively sneezing or coughing, they may still spread viral particles through talking, according to the Centers for Disease Control and Prevention. The CDC encourages everyone to wear face coverings or masks in public to help prevent the spread of the virus.
“Identifying and isolating patients with asymptomatic COVID-19 as early as possible is critical to control the transmission of COVID-19,” the study authors wrote. “Close contacts of patients with COVID-19 should be closely monitored to avoid secondary transmission.”
Based on mathematical modeling, the CDC has estimated 35 percent of COVID-19 cases are asymptomatic.