BEIJING - China has made efforts to prevent the spread of COVID-19 through ports as the country is under pressure to guard against possible imported cases, said the General Administration of Customs (GAC) on Thursday.

The GAC has taken strict measures like health declaration card verification, body temperature monitoring, medical inspections, and virus sequencing at sea, land, and airports.

In addition, the country quickly upgraded prevention and control measures at airports by further strengthening the epidemiological investigations of key populations to curb the spread of the epidemic through entry points.

China has also ramped up the management of crew members of international passenger and cargo flights by implementing health quarantines and sample testing of the crew, said the GAC.

On July 20, nine airport cleaners at the Nanjing Lukou International Airport tested positive for the virus during routine testing. As of Wednesday, Nanjing, the capital of East China's Jiangsu province, has reported a total of 227 locally transmitted confirmed cases.