China requires additional measures for areas with a high risk of spreading COVID-19, said a researcher at a government health agency.

"Places hosting vulnerable groups of people and crowded indoor areas are marked as key areas," said Chang Zhaorui, a researcher with the Chinese Center for Disease Control and Prevention (CDC), at a press conference in Beijing on Wednesday. "These areas are listed in the latest guidelines."

The places hosting vulnerable groups of people include nursing homes, orphanages, schools, logistics companies and hospitals.

Meanwhile, the crowded indoor places include passenger transport terminals, malls, markets, restaurants and bathhouses.

According to Chang, four measures must be taken in the areas that host vulnerable people.

The first is that different divisions should be managed individually to prevent cross-infection.

Second, these areas could face lockdown if the situation gets serious.

The third is designed for the fast-spreading stage of the virus. During that stage, visitors to those areas must reserve first and enter with negative PCR test results obtained 48 hours before entrance. The visitors will have to pass an antigen test before entering the areas.

The last is that the areas must determine the designated hospital they can send infected people to and set up a "green passage" to ensure fast transport of patients.