Delta virus usually refers to the delta strain of novel coronavirus, which usually has more than five characteristics. Novel coronaviruses are RNA viruses and are therefore prone to mutation. 2. Shorter incubation period: Patients infected with the delta strain have a shorter incubation period from the time they are infected by close contact with patients with novel coronavirus pneumonia to the time they develop symptoms compared to the pre-variant strain. 3. High viral load: Patients infected with the delta strain have a higher viral load in their blood. The viral load of patients infected with the Delta strain is higher, so it takes longer to change from positive to negative and the duration of the disease is longer; 5. 7. Atypical symptoms: Some patients have symptoms similar to those of novel coronavirus pneumonia, but some patients may have atypical symptoms after infection, with only symptoms such as malaise, mild muscle aches and olfactory disturbances, or only cold symptoms. The delta strain is a mutation of the novel coronavirus, and the delta strain is susceptible to immune escape, i.e., the vaccine for the novel coronavirus is less protective. However, the new coronavirus vaccine still has some preventive effect against the delta strain, so it is still advisable to actively vaccinate against the new coronavirus to prevent infection.