Wuhan mass screening identifies hundreds of asymptomatic cases

A mass screening program of 10 million Wuhan residents identified 300 asymptomatic cases in May, but none were infectious, according to a new study. Researchers found no 'viable' virus in the asymptomatic cases and the close contacts of these positive asymptomatic cases did not test positive. But these findings do not show that the virus can't be passed on by asymptomatic carriers. Rather, mask-wearing, hand washing, social distancing and lockdown have helped reduce Covid-19 virulence.