People walk on a street in Shanghai, Dec 8, 2022. Scientists have detected XBB.1.5, a new and super-transmissible subvariant of Omicron in the city, but the subvariant, mostly found among the city's imported cases, has yet to cause local transmissions. [Photo/IC]

As more new variants of Omicron emerge in some overseas countries, China has also detected BQ.1 and XBB from imported cases. How virulent are these strains? Will they cause new waves of infections? Here's what Chinese experts are saying.

Q: What are BQ.1 and XBB variants?

A: BQ.1 and XBB are new subvariants of Omicron, which have become dominant in Europe and the US for their increased transmissibility and immune escape capacity, according to Xu Wenbo, head of the China CDC's National Institute for Viral Disease Control and Prevention.

Q: Do the new subvariants have stronger pathogenicity?

A: The virulence of BQ.1 and XBB are no different from other mutant strains of Omicron and rates of severe disease and death have not increased significantly in the countries where BQ.1 and XBB are prevalent, according to Xu.

In the past three months, China has detected BF.7, BQ.1 and XBB from imported cases. But the BQ.1 and XBB have not yet commanded the field in China, where BA.5.2 and BF.7 remain the main strains.

Q: Can people get reinfected by XBB after recovering from previous infections?

A: XBB has a stronger ability to dodge the immune system barriers set up by vaccines and previous infections. With the level of protection decreasing over a period of time after infecting with BA.5, the risk of second-time infection will grow higher when encountering strains with strong immune escape ability, according to Li Tongzeng, chief physician of the respiratory and infectious diseases department of Beijing You An Hospital.

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

Q: Does XBB cause diarrhea?

A: A claim recently went viral online and said the XBB could cause vomiting and diarrhea. On this, Li said some people infected with COVID-19 do have symptoms of vomiting and diarrhea, which can usually go away on their own within one to three days.

However, the XBB strain is not found to be more likely to attack the cardiovascular and cerebrovascular systems and the stomach. Medications for treating respiratory and digestive tract infections can be properly prepared, but there is no need to stockpile them in large quantities.