It is understood that the trajectory of new cases in Mianyang involves many points, affecting schools, custody classes, residential areas in urban-rural fringe and other key places, and it is still possible for control personnel such as close contacts, sub-close contacts and high-risk areas to detect infected people. Wen, deputy director of Mianyang CDC, said: The results of gene sequencing showed that the virus strain that caused the "9.29" epidemic in Fucheng was Omicron mutant strain BA.2.76, which was different from the virus strain found in known provinces and highly homologous to the virus strain in Tibet (mutation site 1), and the traceability work was being stepped up. Combined with the epidemic situation in all parts of the country, the mutant strain BA.2.76 is the most infectious and fastest spreading strain at present. The spread of this strain is more complicated and hidden, and it will become ill within 1-2 days after infection, and it can spread to one generation in less than 2 days. It is speculated that the introduction time of this strain is from September 23rd to 25th.