Many places in North China's Shanxi Province have strengthened prevention and control measures for express delivery firms and employees after the province added four confirmed COVID-19 cases and four silent carriers on Wednesday, all connected to Yunda Express.

Yuncheng city in Shanxi Province ordered Yunda Express couriers in the city to undergo 14-day concentrated isolation after several couriers tested positive for COVID-19. 

All Yunda Express delivery staff in the city are required to follow the 14-day centralized quarantine measures and have been issued with a red health code, the official WeChat account of Yuncheng city said on Thursday. 

The move is aimed at preventing the transmission of virus through post and packages after  36 couriers from Taiyuan Yunda Express in Shanxi tested positive for COVID-19, raising concerns over goods-to-person transmission, officials said.

Family members of Yunda Express staff in Yuncheng are required to adhere to seven-day medical observation at home and have also been issued red health codes. Those who have picked up the deliveries since April 7 must take one nucleic acid test, undertake seven-day self-health monitoring and have been issued with yellow health code. 

Couriers from other logistics firms in the city must take nucleic acid tests on daily basis and immediately report any abnormal results.

Epidemic prevention authorities in Taiyuan, the capital of Shanxi, also issued an urgent notice on Thursday, asking the public to report to their communities or villages immediately if they have received or handled Yunda express packages since April 7.

The official WeChat account belonging to the Shanxi Postal Bureau said that all postal and express delivery companies in the province are operating normally except for the affected sites and personnel linked to Yunda Express.