Covid-19, March 7th, the reporter learned from the news conference of the new crown pneumonia prevention and control work in Xi’an (sixty-third). The virus that caused the local epidemic in Xi’an is a BA2 subtype of the gene. The mutation of the virus has many spots, short latent period, strong infectivity and fast propagation speed. From 0:00 to 9:00 on March 7, Xi’an added four locally confirmed cases. Although they are close contacts of previously confirmed cases, there have been third-generation cases, which fully shows the rapid spread of the virus. Moreover, the transmission of Ba2 subtype in Omicron virus strain is more concealed than that of BA1 subtype, the symptoms are not obvious, and the transmission speed is also increased by 30%. This series of characteristics show that the virus is more likely to cause multi-point sporadic or concentrated outbreaks.