All new arrivals to Shenzhen, Guangdong province, will be required to undergo nucleic acid tests once a day for three days starting Tuesday, as the city adjusted its epidemic prevention and control measures against COVID-19.

The adjustment followed an increase in the number of local infections in the city after the seven-day National Day holiday.

Shenzhen reported 46 locally transmitted COVID-19 cases between Saturday and Monday, of which 32 were linked to people visiting or returning to the city, according to the city's health commission.

On Monday alone, the city reported 14 new locally transmitted confirmed COVID-19 cases and 19 asymptomatic carriers.

Genome sequence results showed there are three main strains of Omicron variants BF.7, BA.2.76 and BA.2.2 in the city's current outbreaks, the Shenzhen Center for Disease Control and Prevention said.

It is the first time the Omicron subvariant BF.7 has been detected in Shenzhen.

Compared with the variants BA.4 and BA.5, BF.7 is characterized by stronger infectivity, ease of diffusion and fast transmission speed, easily causing large-scale outbreaks.

One case with the strain in Shenzhen, who was confirmed to be infected after returning from outside the city, has infected multiple people. Epidemiological investigation showed the citizen did not wear a mask when walking on roads, infecting several passersby.