A medical worker collects a swab sample of a resident for nucleic acid testing at a community in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative. (Photos: Xinhua)

Aerial photo shows residents queuing up to take swab sample for nucleic acid testing at a community in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.

Aerial photo shows students queuing up to take swab sample for nucleic acid testing at a primary school in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.

A medical worker collects a swab sample of a resident for nucleic acid testing at a community in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.

A medical worker collects a swab sample of a student for nucleic acid testing at a primary school in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.

A medical worker collects a swab sample of a student for nucleic acid testing at a primary school in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.

Aerial photo shows residents queuing up to take swab sample for nucleic acid testing at a community in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.

Aerial photo shows students queuing up to take swab sample for nucleic acid testing at a primary school in Lu'an, east China's Anhui Province, May 22, 2021. From 2 p.m. Saturday until Monday, Lu'an will conduct a third round of nucleic acid testing for residents in the main districts and key areas, said the municipal health commission. Lu'an started its second round of COVID-19 testing on May 17. As of May 19, a total of 1,050,298 samples had been tested, all of which came back negative.