Omicron new subvariants BQ.1 and XBB, which have been detected in Shanghai in imported cases under closed-loop management, have not caused local transmission yet, said Yuan Zhengan, a member of the city's expert advisory group on COVID-19 prevention.

Ling Yun, deputy director of the Shanghai Public Health Clinical Center, also confirmed that as a designated hospital to treat overseas arrivals who are infected with COVID-19, the center is implementing strict closed-loop management for the confirmed cases, and the patients will only be released from quarantine after meeting the criteria for discharge from hospital, so the two mutant strains have not spread locally.

BQ.1 and XBB are new subvariants of Omicron, and they are circulating in some overseas countries and regions including the U.S. and Europe for their increased transmissibility and immune escape capacity.

A screenshot introducing XBB.1.5 variant prevailed on Chinese social media on Saturday, saying the variant mainly attacks heart, blood vessels and stomach and suggested preparing Montmorillonite powder for diarrhea caused by the variant.

The screenshot led to sold-out of the medicine at many pharmacies in Beijing, Shanghai and Shenzhen on Sunday.

There's no need to hoard the medicine, said Li Tongzeng, doctor from the Department of Respiratory and Infectious Diseases at Beijing You'an Hospital. He noted there is no evidence that XBB.1.5 is more likely to invade the cardiovascular and cerebrovascular systems or digestive systems, the People's Daily reported on Monday.