According to the research results published by South China Agricultural University, a virus carried by pangolin is highly similar to that of novel coronavirus, and the 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?

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

After years of tracing the family history of virologica sinica, it is 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 infect civets with a coronavirus, and then the virus mutates in civets, enabling them to infect humans and eventually become SARS virus.

With previous experience, when tracing back to the origin of COVID-19, scientists naturally thought of bats again. According to the gene sequencing results of Shi's research team [1], the sequence similarity of bat coronavirus TG 13 with [is 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 between the bat coronavirus TG 13 and COVID-19 in the S 1 receptor binding domain is not so high, which means that it is difficult for bat coronavirus to directly infect humans. Bat coronaviruses need to undergo genetic variation in intermediate hosts, such as gene recombination, so that they will become more susceptible to human infection.

During the spread of COVID-19, bats came into contact with potential intermediate hosts such as pangolins, and the coronavirus from bats spread to pangolins across races, constantly evolving. When humans come into contact with these infected pangolins, the mutated coronavirus may invade human cells, thus infecting humans and becoming the 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-Shi Li et al., discovered a novel coronavirus and its potential bat source related to the recent outbreak of human pneumonia, bioRxiv, 2020, DOI:10.1012020.0/kl.