Thousands of asymptomatic, mild coronavirus cases weren't detected in Wuhan, Chinese study shows

The virus has infected nearly 430,000 people and killed more than 19,000

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China lifted tough restrictions on the province at the epicentre of the coronavirus outbreak on March 25 after a months-long lockdown
China lifted tough restrictions on the province at the epicentre of the coronavirus outbreak on March 25 after a months-long lockdown Credit: STR/AFP via Getty Images

Chinese researchers say that 59 per cent of people who contracted the novel coronavirus in the city of Wuhan, the epicentre of the outbreak, had mild or no symptoms and didn’t report for medical assistance.

That means thousands of infections likely fell under the radar, and were never included in the government’s official count, according to a study led by doctors at Huazhong University of Science and Technology in Wuhan, with collaboration from experts from Fudan University and Harvard University.

“Unascertained cases included asymptomatic cases and those with mild symptoms who could recover without seeking medical care and thus were not reported to authorities,”  the researchers wrote in the study, not peer-reviewed and published online earlier this month on MedRxiv. 

“We assumed only those seeking medical care would be reported and quarantined by hospitalisation.”

There is “increasing evidence” to suggest that people contracting the virus with mild or no symptoms can be infectious to others, which is “imposing a substantial challenge to the epidemic control.” 

It also throws into question understanding of how much an entire population could be affected by disease spread. 

The estimate was based on nearly 26,000 lab-confirmed coronavirus cases reported in Wuhan through February 18. 

The coronavirus pandemic first erupted in central China late last year, and has spread quickly around the world, infecting nearly 430,000 people and killing more than 19,000, according to data collected by Johns Hopkins University.