China has reported 21 new COVID-19 infections, including 13 asymptomatic ones, taking the number of cases in the country to 82,941, health authorities said on Saturday, as Wuhan city, where the outbreak originated, ramped up efforts for the mass testing of its 11 million residents.
China's National Health Commission (NHC) said that of the eight new confirmed COVID-19 cases reported on Friday, six were imported infections.
The other two cases are both domestically transmitted and reported in Jilin Province, which recently went into lockdown mode after reporting a cluster of cases, it said.
But the numbers of asymptomatic cases continued to increase as 13 more cases were reported on Friday. The NHC said that 561 asymptomatic cases, including 30 from overseas, were still under medical observation.
Asymptomatic cases are a problem as the patients are tested COVID-19 positive but develop no symptoms such as fever, cough or sore throat. However, they pose a risk of spreading the disease to others.
The central Hubei province and its capital Wuhan, where the COVID-19 originated late last year, reported 439 asymptomatic cases till Friday, prompting Chinese officials to resort to mass testing of 11 million residents of the city beginning from Wednesday.
Hubei health commission said on Saturday that a total of 283,405 close contacts of COVID-19 patients in the province had been tracked by Friday, 763 of whom were still under medical observation.
By Friday, death toll from the virus in the province stood at 4,512, including 3,869 in Wuhan.
Hubei had so far reported 68,134 confirmed COVID-19 cases in total, including 50,339 in Wuhan.
As of Friday, the overall confirmed cases on the mainland had reached 82,941, including 89 patients who were still being treated, and 78,219 people who had been discharged after recovery, the NHC said.
Altogether, 4,633 people have died of the disease, it said.
Explaining the reason for testing all 11 million residents of Wuhan after lifting of its over a month lockdown, Zeng Yixin, deputy head of the NHC told the media that mass nucleic acid testing on all residents in Wuhan for COVID-19 will help protect people's health and fully resume social and economic order in the city.
The mass testing is conducive to learning more about the scope of the epidemic in the city and carrying out targeted epidemic control and prevention measures, he said.
Conducting nucleic acid tests on all Wuhan residents is no easy task in terms of mobilisation and organisation, Zeng said.
"We need to make sure people who have been tested earlier do not have close contact with those who will be tested later, and the accuracy of the test shall not be undermined by the large number of tests," he said.
Wuhan conducted nucleic acid tests on more than three million residents earlier and will carry out the test on all residents that have not been tested before, according to a notice issued by the local authorities on Thursday.
Residents living in old and populous communities and communities with previous confirmed cases will be tested first, it said, adding that the local government will shoulder the costs for the tests.