Authorities in the Chinese city of Wuhan said they had tested almost 10 million people for COVID-19 over 19 days and found 300 asymptomatic infections, state media reported on Tuesday.
The people found with asymptomatic infections were isolated, and 1,174 of their close contacts were put under observation, the state-run newspaper People’s Daily said.
No confirmed coronavirus cases were found during the testing period, which ended on Monday, the paper said.
Chinese authorities categorise as confirmed coronavirus cases patients who have both tested positive and shown symptoms such as a cough and fever.
Authorities in Wuhan, where the coronavirus first broke out in December, pledged to test all of the city’s 11 million residents starting on May 14.
The mass testing was intended to assuage public concerns after a cluster of six new cases were reported in the city following 35 days of no new reported infections.
Authorities used sample pooling, in which they collected individual samples but processed up to 10 of them together in a single nucleic-acid test.
The same method has been used in the United States and Germany to track coronavirus cases albeit on a smaller scale.
China on Tuesday said it was monitoring 73 active coronavirus cases across the country, including five new infections identified over the previous day among travelers returning from abroad.