The most stunning example of this came from a city-wide screening for Sars-Cov-2 in May in Wuhan, China, where the virus apparently originated. Researchers tried to test everyone in Wuhan. They nearly succeeded, carrying out almost 10 million tests. They found 303 people who tested positive for the virus. All 303 cases were asymptomatic. The scientists then traced 1174 close contacts of those people – and found not one had been infected. “There was no evidence of transmission from asymptomatic positive persons,” they wrote.
