Delta mutant is the main strain of COVID-19 epidemic worldwide at present. In September, 2020, the Delta mutant was first discovered in COVID-19 cases reported in India. 202 1, 10 In May, the World Health Organization announced that Delta mutant was included in the list of COVID-19 mutants that need to be paid attention to globally. At present, it has been prevalent in 130 countries and regions, and has become the main virus strain of COVID-19 epidemic worldwide.
Compared with previous strains, this strain has stronger infectivity and transmission ability, shorter incubation period or passage interval, and has the characteristics of faster transmission speed, higher viral load, faster replication in vivo and longer negative conversion time.
Relevant scientific research and epidemic prevention and control practices at home and abroad show that Delta mutation has not caused subversive changes in COVID-19's biological characteristics, and the source of infection and transmission route are basically clear. The existing epidemic prevention and control measures are still effective for Delta mutant. The existing vaccines still have good preventive and protective effects, which can reduce the risk of virus transmission in people, reduce the transmission power of infected people, and effectively reduce the incidence and mortality of severe illness after infection. Some time ago, China successfully blocked the spread of Delta mutant in several densely populated and mobile cities in Guangdong Province for the first time, which proved that measures such as vaccination, wearing masks, washing hands frequently, keeping social distance and avoiding crowd gathering were effective.