Shanghai steps up virus fight

Separately, Northeast China's Jilin province reported 956 confirmed cases and 3,499 asymptomatic carriers on Saturday, the provincial health commission said. The province has reported more than 50,000 infections since March.

The commission said the situation in Changchun, the provincial capital, was still developing, while the situation in Jilin city was improving as infections in the past week dropped by 44 percent compared to a week before.

On Saturday, Suzhou, Jiangsu province, reported a new Omicron subvariant BA.1.1. The city's center for disease control and prevention said that no highly homologous sequence of the novel coronavirus genome was found in multiple databases.

The center said that it will take more time to analyze and compare the subvariant.

It is important to collect samples from current COVID-19 infections, conduct genome sequencing and closely monitor the mutation situation. It is also necessary to detect mainstream virus strains in a timely manner, and develop effective vaccines, antiviral drugs and detection reagents.

Experts said a new subvariant does not always mean a more contagious strain, and only the most adaptable ones survive. However, some subvariants can become the main strain of a virus.