A medical worker in a protective suit conducts a nucleic acid testing for a resident at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 14, 2020.

A medical worker in protective suit conducts nucleic acid testings for residents at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Medical workers in protective suits conduct nucleic acid testings for residents at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Medical workers in protective suits conduct nucleic acid testings for residents at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Residents line up for nucleic acid testings at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Residents wearing face masks line up for nucleic acid testings at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Residents wearing face masks line up for nucleic acid testings at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Image used for illustrative purpose. Workers in protective suits collect swabs from senior high school students for nucleic acid tests at Hubei Wuchang Experimental High School before the students are set to return to campus on May 6, in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, in China's Hubei province April 30, 2020. cnsphoto via REUTERS

Residents wearing face masks line up for nucleic acid testings at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

Residents line up for nucleic acid testings at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 15, 2020.

A medical worker in a protective suit conducts a nucleic acid testing for a resident as people wearing face masks queue behind for testings, at a residential compound in Wuhan, the Chinese city hit hardest by the coronavirus disease (COVID-19) outbreak, Hubei province, China May 14, 2020.