Recently, the COVID-19 XBB.1.5 strain has attracted attention. How about the existence of this strain in China? Will it lead to the second round of infection of COVID-19? On January 4, in response to social concerns, the Institute of Viral Diseases of the Chinese Center for Disease Control and Prevention issued a document stating that XBB. 1.5 local cases have not been detected in China's local cases for the time being, and the current epidemic strains in China are still dominated by BA. 5.2 and BF. 7, sub branches of BA. 5. At the same time, there is no evidence that the evolutionary branch of XBB. 1.5 is more likely to cause severe diarrhea or other clinical manifestations of gastrointestinal tract than other strains. The possibility of large-scale epidemic caused by XBB series mutants, including XBB. 1.5, is low in China in the short term. It is understood that XBB. 1.5 has gradually increased in the proportion of COVID-19 infected people in the United States since November 2022. According to the prediction of weekly surveillance cases in the United States, the proportion of XBB. 1.5 has reached 40.5% on December 30, which may replace BQ. 1.1 and BQ. 1 and become the dominant epidemic strain in the United States. As of January 2, 2023, XBB. 1.5 has been monitored in at least 25 countries and regions around the world. At present, what is the situation of XBB. 1.5 in China? In this regard, experts from CDC said that 199 cases of XBB import have been found in China through genome sequencing from October to December 2022, including 9 sub branches, of which 4 cases are XBB 1.5 import cases. From October to December 2022, a total of 16 local XBB cases were reported, all of which were evolutionary branches of XBB. 1, and were mainly concentrated in October to November. In December, there was only one local case. No local case of XBB. 1.5 was detected. In response to the public's concern about whether XBB 1.5 will attack the human intestinal tract and other issues, experts from CDC explained that as the main receptor of COVID-19 binding cells, angiotensin converting enzyme 2 (ACE2) has a high content in the intestinal tract in addition to being expressed in the lungs. All variants of COVID-19, including XBB series variants, will infect intestinal mucosal cells, but due to individual differences, The presence or absence of intestinal clinical symptoms is related to individual differences. For the evolutionary branch of XBB. 1.5, which has been concerned recently, there is no evidence that it is more likely to cause severe diarrhea or other clinical manifestations of gastrointestinal tract than other strains. Does XBB. 1.5 cause the second round of infection of COVID-19? Experts said that it was reported that XBB. 1.5 may have a strong immune escape ability, causing international concern. However, the monitoring data from the US Centers for Disease Control and Prevention confirmed that during the period of increasing the proportion of XBB series mutants in recent weeks, the number of reported cases, hospitalized cases and deaths of COVID-19 infection did not increase significantly. At present, the absolute dominant strains prevalent in China are BA. 5.2 and BF. 7. Neutralizing antibodies produced by individuals infected with BA. 5.2 or BF. 7 will maintain a relatively high level in a short period of time (3 months). It is expected to have a better cross protection effect on other branches of Omicron mutant (including XBB). In the short term (3 months) in China, the variation is from XBB series