At present, the Delta virus strain has rapidly become a popular strain. According to reports, Zhong Nanshan, an academician of the Chinese Academy of Engineering, and other teams have accurately described the complete transmission chain of Delta mutant for the first time in the world. The research also revealed that Delta has the characteristics of short-latency, fast transmission, high viral load, long negative time of nucleic acid and easy development to critical illness.
According to CCTV news reports, the team of Professor Tang Xiaoping and Professor Li Feng from the Eighth Affiliated Hospital of Guangzhou Medical University, together with the team of Academician Zhong Nanshan and Professor Chen Ruchong from Guangzhou Respiratory Health Research Institute of the First Affiliated Hospital of Guangzhou Medical University, combined with epidemiology and virus genome sequencing technology, accurately described the complete transmission chain of Delta variant strain in the world for the first time and combined with clinical resources, described the clinical features and virus dynamics of the cases in the epidemic.
According to previous epidemiological investigations and viral nucleic acid gene sequencing, the “5.21 COVID-19 outbreak” was caused by Delta, and its transmission chain was clear. For the first time, this study tracked and completely reported the clear chain of transmission of the epidemic. At the beginning of the epidemic, a 75-year-old woman was infected by accidental exposure, and three others were infected by close family contact or dinner. The researchers observed that the transmission route of the virus in the epidemic was mainly through direct and indirect close contact, in which 30.8% of infected people were transmitted through meals, followed by family contact (30.13%), community transmission (18.59%) and other transmission routes including work and social contact (19.87%).
At the same time, the researchers included those infected with the “May 21” epidemic into the queue of patients infected with wild virus strains in novel coronavirus in 2020, analyzed the clinical features and virus dynamics of the “May 21” epidemic cases from various aspects, summarized the characteristics of Delta, and searched for the risk factors for developing into severe cases.
The researchers have found that Delta has a short delay time and fast transmission speed. The median incubation period was only 4.7 days, which was obviously shorter than that of wild strains (6.3 days). Further subgroup analysis showed that the virus latency (4.0 days) of Delta patients in the non-severe group was significantly shorter than that of wild strains (6.0 days). Delta can be transmitted for 4 generations within 10 days, and the fastest transmission between generations is no more than 24 hours.
