Tracing back to the source, where did COVID-19 originally come from?

According to the research results published by South China Agricultural University, a virus carried by pangolin is highly similar to novel coronavirus, and its sequence consistency is as high as 99%. Such high similarity means that the intermediate host of COVID-19 may be pangolin.

If pangolins are possible intermediate hosts, how did the virus on them come from in the first place?

Regarding the origin of COVID-19, we can refer to the SARS coronavirus of that year. Both viruses are coronaviruses, and the sequence similarity between them is 79.5%. According to the analysis, SARS virus was transmitted from civet cats to humans. However, civet cats are not the source of infection, but an intermediate host.

After years of follow-up research, the family history of virologica sinica finally found that the gene sequence of SARS virus can be found in a remote bat cave, and the Chinese chrysanthemum bat living there is probably the original source of SARS virus. Bats first spread a coronavirus to civets, and then the virus mutated in civets, enabling them to infect humans and eventually become SARS virus.

With previous experience, when tracing the origin of COVID-19, scientists will naturally think of bats again. According to the gene sequencing results of Shi's research team [1], the sequence similarity of bat coronavirus TG 13 with [was 96.2%. Therefore, the coronavirus in bats may also be the source of COVID-19.

Bats carry a lot of viruses. Ebola virus, MERS virus, rabies virus, SARS virus and other viruses are all considered to come from bats. But there are many DNA repair genes in bats, which can inhibit the viruses in them, so bats carrying many viruses often don't get sick.

The sequence similarity of bat coronavirus TG 13 and COVID-19 in S 1 receptor binding domain is not very high, which means that bat coronavirus is difficult to directly infect humans. Bat coronaviruses need to undergo genetic variation in intermediate hosts, such as gene recombination, so that they will be more likely to infect humans.

During the transmission in COVID-19, bats came into contact with potential intermediate hosts such as pangolins, and coronavirus from bats spread to pangolins across races, and constantly mutated and evolved. When humans come into contact with these infected pangolins, the mutated coronavirus may invade human cells, thus infecting humans and becoming a previously unknown COVID-19.

In a word, wild animals are natural and intermediate hosts of COVID-19 and many other viruses. Only by refusing to kill and eat them can we stop the spread of the virus from the source.

refer to

[1] Zheng, et al. Found a novel coronavirus and its potential bat source related to the recent human pneumonia epidemic, bioRxiv, 2020, DOI:10.1012020.0/kloc.