A resident is being vaccinated with COVID-19 vaccine in Zhongshan, South China's Guangdong Province on June 23, 2021. Photo: CFP

Zhongshan, in South China's Guangdong Province, announced that it would launch mass nucleic acid testing for COVID-19 and restrict transportation on Thursday after one positive case was found to be related to the recent small-scale outbreak at an international airport in Nanjing, East China's Jiangsu Province.

Starting on Friday, a certificate with negative nucleic acid test results taken within 48 hours is required for departure from the airport and at railway and highway stations in the city. 

Zhongshan authorities reported one COVID-19 asymptomatic patient on Thursday, who had flown to Nanjing Lukou International Airport on July 15, and left Nanjing from the airport on Monday. 

The 23-year-old female was found to be infected with the virus on Thursday during the testing that Zhongshan government had organized for people with a history of travel to epidemic affected regions in China. 

The city government has suspended the operation of indoor venues, wholesale markets and training institutions in the district where the patient lives.

Nanjing on Tuesday night reported that nine cleaning staff at Lukou International Airport had tested positive for COVID-19. As of Thursday afternoon, there are 13 confirmed cases and nine asymptomatic patients in the city. 

Nanjing launched citywide nucleic acid testing on Wednesday.