China has stepped up COVID-19 testing and genome sequencing of inbound travelers, patients visiting hospitals and other key groups to closely monitor viral mutations, officials said on Sunday.

Yang Feng, an official with the National Administration of Disease Prevention and Control, said that as China's COVID-19 control work enters a new phase, it has strengthened cooperation with customs authorities to keep track of imported infections.

Meanwhile, each provincial-level region is required to designate sentinel hospitals which will collect samples and analyze genome sequencing of some local infections, severe cases and deaths, so as to identify trends of emerging variants and catch new strains in a timely manner.

As the XBB strain, a highly immune-evasive strain, is threatening to dominant circulation in the United States and spread fast globally, Chen Cao, a researcher from the Chinese Center for Disease Control and Prevention, said that China has detected 16 locally transmitted infections of XBB since August 1.

Although XBB is more capable of evading existing immunity and thus transmitting quickly, Chen said available research shows that its pathogenicity — ability to induce severe cases and deaths — is not stronger.

Chen added that the XBB strain has not gained advantage in the domestic spread of the disease over the dominant strains of BA.5.2 and BF.7 in China.

As immunity gained from a previous infection can last for as long as six months and can also protect against new variants, he said XBB will not spark large domestic outbreaks.

"China has strengthened the surveillance of viral mutations and is able to detect and analyze the risk of imported infections of new strains," he said, adding that emergency plans to handle new strains have also been formulated.