Between 40% and 45% of COVID-19 infections could be in people who display no symptoms of the illness, according to an analysis by Scripps Research published in Annals of Internal Medicine.
The findings reveal that asymptomatic people could play a larger role in the spread of the virus than previously thought. The World Health Organization has flip-flopped about whether the spread of COVID-19 through asymptomatic people is rare or common.
“The silent spread of the virus makes it all the more challenging to control,” Eric Topol, MD, founder and director of the Scripps Research Translational Institute and professor of Molecular Medicine at Scripps Research, said in a statement. “Our review really highlights the importance of testing. It’s clear that with such a high asymptomatic rate, we need to cast a very wide net, otherwise the virus will continue to evade us.”
Topol and behavioral scientist Daniel Oran collected information from 16 cohorts, using datasets gathered from keyword searches of PubMed, bioRxiv and medRxiv and Google searches of new reports about COVID-19. Their review found that asymptomatic people may actually make up a large chunk of total infection and contribute greatly to the spread of the virus. In addition, asymptomatic people may be able to spread the virus for longer than 14 days.
“What virtually all of them had in common was that a very large proportion of infected individuals had no symptoms,” Oran said. “Among more than 3,000 prison inmates in four states who tested positive for the coronavirus, the figure was astronomical: 96 [%] asymptomatic.”
However, it is not clear whether the infectiousness is the same magnitude among symptomatic and asymptomatic people, despite having the same viral loads, the researchers found. On CT scans performed revealed significant subclinical lung abnormalities in 54% of the 76 asymptomatic patients from the Diamond Princess cruise ship included in the study, indicating infection that might impact lung function, even if not immediately apparent.
“Our estimate of 40 to 45 [%] asymptomatic means that, if you’re unlucky enough to get infected, the probability is almost a flip of a coin on whether you’re going to have symptoms,” Oran said. “So, to protect others, we think that wearing a mask makes a lot of sense."
Researchers noted that more testing is needed.
Amy joined TriMed Media as a Senior Writer for HealthExec after covering home care for three years. When not writing about all things healthcare, she fulfills her lifelong dream of becoming a pirate by sailing in regattas and enjoying rum. Fun fact: she sailed 333 miles across Lake Michigan in the Chicago Yacht Club "Race to Mackinac."