Mild, asymptomatic or otherwise unrecognized infections may have driven the rapid spread of the novel coronavirus in the outbreak’s earliest days, according to modeling published Monday in the journal Science.
The research, based on reported cases in China and travel data, estimated that 86% of coronavirus infections in the country were “undocumented” in the weeks before officials instituted stringent quarantines.
Undocumented infections, according to the researchers, can go unrecognized because they come with mild or no symptoms, and that “can expose a far greater portion of the population to virus than would otherwise occur.”
These undetected cases, which are often less severe, were estimated to be about half as contagious as confirmed cases. But because undetected cases were more common, they could have played an outsize role in spreading the virus, the study said.
About 4 in 5 people confirmed to have coronavirus, for example, were likely infected by people who didn’t know they had it, according to the modeling.
“These findings explain the rapid geographic spread of [coronavirus] and indicate containment of this virus will be particularly challenging,” the researchers wrote.
The study, they later added, suggests that “a radical increase in the identification and isolation of currently undocumented infections would be needed to fully control [the virus].”