Shanghai Friday reported 83 new local COVID-19 cases, of which 78 were asymptomatic, according to the municipal health commission.

Four of the confirmed cases plus 57 asymptomatic cases were close contacts of previously reported infections. These cases were found during quarantine. The rest cases were found when conducting tests among people with risk of exposure to COVID-19.

Also on Friday, the city reported 31 imported cases, nine of which were asymptomatic. All of the close contacts of the new cases were put in quarantine.

On another front, the National Health Commission said in a notice on Friday that China will begin using COVID-19 antigen tests as a supplementary method to improve its early detection capability.

The antigen test is less accurate compared to the nucleic test, while nucleic test can discover infections once one was infected with the virus, said Zhang Wenhong, leader of the Shanghai team of experts in the treatment of COVID-19, during an interview with Shanghai Television Station.

However, the antigen test gives results more quickly than the nucleic test currently in use, which is more convenient for use. It is very helpful considering that most cases are asymptomatic.

"Antigen tests cost less and can be used at home or at hospital without nucleic acid analyzing device," zhang said. "It will help us keep abreast with the transmission of the virus and control the spread in a relatively low level."