国内已监测到XBB毒株，会二次感染吗？专家解读

BQ.1 and XBB are new subvariants of Omicron which have become the dominant strains in some overseas countries and regions for their increased transmissibility and immune escape capacity. 

Their virulence is no different from other mutant strains of Omicron and the rate of severe illness and mortality rate have not increased significantly in the countries where BQ.1 and XBB are prevalent, according to Xu Wenbo, director of Institute of Viral Diseases, Chinese Center for Disease Control and Prevention. 

Samples randomly collected from COVID-19 patients in Shanghai between Nov 23 and Dec 22 in 2022 showed that apart from the BA.5.2 variant spreading in southern China and the BF.7 variant spreading in the northern region, Omicron subvariants BQ.1 and XBB widely spread in some overseas countries have also been found in Shanghai. 

"At present, the immune escape capacity of XBB strain has enhanced, which is different from that of the BA.5 variant prevailing in our country. The level of protection decreased over a period of time after infecting with BA.5, thus there is an increasing risk of reinfection when encountering strains with strong immune escape capacity," said Li Tongzeng, doctor from the Department of Respiratory and Infectious Diseases at Beijing You'an Hospital.

However, reinfection occurs mainly in people with poor immunity and people with normal immune function are less likely to be reinfected in a short period of time and the symptoms after infection are usually milder than the first time, Li added. 

Despite that some people infected with COVID-19 do experience vomiting and diarrhea, the symptoms usually relieve spontaneously within one to three days. 

Medications for respiratory and digestive tract infections can be properly prepared but there's no need to hoard the medicine, Li said, noting there is no discovery of XBB.1.5 to be more likely to invade the cardiovascular and cerebrovascular systems or digestive systems.