A mass screening program of 10 million residents following a lockdown lift in Wuhan, China, found 300 people with asymptomatic cases, none of whom were infectious, researchers reported in Nature Communications.
Wuhan had a strict lockdown to control the coronavirus and lifted restrictions in early April. The study looked at test results in the last two weeks of May to examine the effectiveness of the lockdown and practices aimed at curbing disease spread, such as hand-washing, mask wearing, and social distancing. The asymptomatic cases were not deemed to be infectious based on virus cultures and none of the 1,174 contacts of asymptomatic people tested positive for coronavirus, reported researchers from the Huazhong University of Science and Technology in Wuhan and the University of East Anglia in England on November 20.
It's possible for asymptomatic people to transmit the virus, but the measures taken in Wuhan have been effective for limiting spread in this way, the researchers concluded, noting that mask wearing is common.