A mass screening program of 10 million Wuhan residents identified 300 asymptomatic cases in May, but none were infectious, according to a new study.
"This screening programme identified 300 asymptomatic cases. But the virus cultures indicated no viable virus in the identified asymptomatic cases. This means that these people were not likely to infect anyone else."
https://www.sciencedaily.com/releases/2020/11/201130131511.htm