(Fighting New Coronary Pneumonia) Zhong Nanshan and other teams accurately described the Delta transmission chain and found that the median incubation period of Delta is only 4.7 days

  China News Service, Guangzhou, September 15 (Cai Minjie, Liu Qisha) The Eighth Municipal Hospital of Guangzhou Medical University stated on the 15th that the team of Professor Tang Xiaoping and Li Feng of the hospital had joined forces with the Guangzhou Medical University First Affiliated Hospital, Guangzhou Institute of Respiratory Health, and Zhong Nanshan, academician, The team of Professor Ruchong Chen, in response to the "5.21 New Coronary Pneumonia Epidemic" caused by the Delta mutant, combined epidemiology and viral genome sequencing technology to accurately describe the complete transmission chain of the Delta mutant spread on a global scale for the first time.

  The above research results were recently published in the international journal "The Lancet" sub-issue "Journal of Electronic Clinical Medicine".

  Data from the health system at home and abroad preliminarily show that the Delta variant strain has a strong transmission capacity, but the epidemiological and clinical characteristics of the new crown patients infected with the Delta variant strain are temporarily unclear.

  Recently, the new crown epidemic broke out in Guangdong, centered on Guangzhou. As of June 23, 4 cities were involved, with a total of 167 confirmed cases.

According to epidemiological tracking and sequencing analysis, it is clear that the epidemic is a Delta variant infection cluster with a clear chain of transmission.

  In response to this outbreak, the above team described the complete transmission chain of the Delta mutant strain for the first time, and also included the cohort of the wild strain of the new coronavirus in the 2020 new crown epidemic for research, and analyzed the 159 outbreaks in Guangzhou from a multi-faceted perspective. The clinical characteristics and viral dynamics characteristics of each case of Delta variant strains, seeking risk factors for progression to severe illness.

The results showed that the Delta mutant strain spreads faster, the incubation period is shorter, the viral load is higher, and the virus clearance time is longer. Infection with the Delta mutant strain is a risk factor for the development of critical illness.

  On May 21, 2021, the Guangdong Provincial Center for Disease Control confirmed the first 75-year-old female patient with new coronary pneumonia.

According to previous epidemiological investigations and viral nucleic acid gene sequencing, the "5.21 New Coronary Pneumonia Outbreak" was caused by the Delta mutant strain and has a clear chain of transmission.

This study tracked and fully reported the clear transmission chain of local cases in Guangzhou in 2021 for the first time.

The main route of transmission of the virus is through direct and indirect contact. Among them, co-dining accounted for the highest proportion (31.41%), followed by family contact (30.13%), community transmission (18.59%), and work and social contact. Other means of transmission (19.87%).

  This study showed that the incubation period of the Delta mutant strain was short and the spread speed was fast. The median incubation period was only 4.7 days, which was significantly shorter than that of the wild strain (6.3 days).

Further subgroup analysis showed that in the non-critical group, the virus incubation period (4.0 days) of the Delta mutant strain was significantly shorter than that of the wild strain (6.0 days).

Delta mutant strains can be transmitted for 4 generations within 10 days, and the fastest intergenerational transmission does not exceed 24 hours.

  Compared with the wild strain, the viral load of those infected with the Delta mutant strain was significantly higher (the median CT value of the former was 34.0, and the latter was 20.6. The lower the CT value indicates the higher the viral load), those infected with the Delta mutant strain The time for nucleic acid to become negative is also significantly longer than that of wild strains.

  The researchers also found that infection with the Delta variant strain is a risk factor predicting that the disease will turn into a critical illness.

Among elderly patients with new coronary pneumonia aged 60 and over, the Delta variant strain group has a 1.45 times higher risk of critical illness than the wild strain group; and infection with the Delta variant strain develops into a critical illness 2.98 times faster than the wild strain.

  This study believes that rapid tracking, isolation and timely detection of virus infections, restrictions on the social environment and city-wide nucleic acid screening are very important, and these measures quickly cut off the source of infection.