Variant viruses belong to the Neocoronavirus, which is just a mutation based on the original strain of Neocoronavirus. At present, there are three variant strains of neocoronaviruses that have received attention, the most important of which is the Delta variant virus, which has gradually become the mainstream strain worldwide due to its strong infectivity and fast transmission speed. The following is a brief introduction of the Delta variant virus, for example, in terms of its transmission ability, virulence, and concealment, etc.: 1, Transmission Ability: The Delta variant virus has a much stronger transmission ability compared to the original strain of neocoronaviruses The transmission index is 5-8, which means that one case can infect 5-8 people, and the transmission index even reaches 9-10 in some areas, which is much higher than that of the original strain, which is 2.4-2.6. 2. Virulence: The respiratory viral load of Delta mutant virus is 1260 times higher than that of the original strain of Neocoronavirus, and the increase in respiratory viral load is related to the increase in the proportion of severe illnesses and mortality rate, which indicates that Delta mutant virus has a stronger transmission ability than the original strain of Neocoronavirus. The increased respiratory viral load is associated with higher rates of severe illness and mortality, indicating that the increased virulence of delta variant virus has a shorter incubation period and faster onset of illness; 3. Concealment: the original strain of neocoronavirus can be detected in the human body for a period of 6 days in general, whereas the delta variant virus has a higher degree of concealment, is not easy to detect, and may require multiple nucleic acid tests.