The Delta/δ strain is one of the most important viral mutations in the current global new crown epidemic. From the perspective of previous related epidemics, the Delta strain is characterized by high transmission capacity, rapid transmission, and increased viral load: 1. Alpha strain has increased its transmission capacity by more than 40%. 2. Rapid transmission: The incubation period and transmission interval of the Delta strain have been shortened after infection, and if preventive and control measures are not in place and the immune barrier is not formed by vaccination, the multiplication rate of the epidemic development will be significant. This corresponds to an increase of 2-3 times the number of patients every 4-6 days for previous strain infections and 6-7 times the number of patients in about 3 days for the Delta strain.3. Increase in viral load: The results of virus detection by PCR show a significant increase in the viral load in the patient. This means that the proportion of patients who turn heavy and critical after the onset of the disease is higher than before, while the time to turn heavy and critical is earlier and the time needed for the patient to be treated with nucleic acid conversion will be longer. Although the delta strain may have immune escape and partially avoid neutralizing antibodies to suppress the immune response, the proportion of unvaccinated people in the confirmed cases who became severe or developed severe disease was significantly higher than that of vaccinated people, indicating that the commonly used domestic vaccines are still effective against the delta strain.