Stop the virus, why should we fast wild animals？

　　A few days ago, the National People’s Congress Standing Committee (NPCSC) voted to completely ban illegal wildlife trade, get rid of the bad habit of eating wild animals, and effectively protect people’s lives, health and safety.

　　This decision is obviously closely related to the COVID-19 epidemic. So, what is the relationship between Covid-19 transmission and wildlife?

　　Let’s sort out the recent related scientific research results.

　　On February 24th, a piece of news caught people’s attention. The National People’s Congress Standing Committee (NPCSC) voted to pass a decision on completely banning illegal wildlife trade, getting rid of the bad habit of eating wild animals, and effectively protecting people’s lives, health and safety. A system of completely prohibiting the consumption of wild animals has been established. In violation of the existing laws and regulations, the punishment should be aggravated on the basis of the existing laws.

　　At present, under the situation that the whole country is playing chess and fighting against the COVID-19 epidemic, this decision is obviously closely related to the COVID-19 epidemic.

　　Bats may be the source of Covid-19.

　　Humans are no strangers to infectious diseases caused by coronavirus. The SARS coronavirus, which was prevalent in winter of 2002 to 2003, was confirmed to have originated from the natural host bat, passed through the intermediate host civet cats and then passed on to humans. MERS coronavirus discovered in 2012, namely Middle East respiratory syndrome coronavirus, was also considered to have originated from natural host bats and spread to humans through intermediate host camels.

　　Since the winter of 2019, novel coronavirus, whose infection scale far exceeds that of SARS and MERS, has been transmitted to human beings through what channels?

　　Because of the lessons of SARS and MERS, scientists naturally set their sights on bats first.

　　Shi Zhengli’s team from Wuhan Institute of Virology, Chinese Academy of Sciences published a paper in the form of preprint on bioRxiv website on January 23rd, and this paper was published online by the top academic journal Nature on February 3rd. In this paper, the research team compared the novel coronavirus genome extracted from patients with severe pneumonia with the coronavirus gene sequence carried by a bat in the early laboratory, and found that the whole genome sequence of RaTG13 coronavirus in this bat was as consistent as 96.2% with novel coronavirus infected by human.

　　This means that the natural host of Wuhan novel coronavirus is probably a bat!

　　RaTG13, a virus closely related to bats, is the ancestral virus of novel coronavirus, which is derived from a coronavirus of China Jutoubat, which was discovered by Shi Zhengli’s team when sampling in Yunnan.

　　Moreover, novel coronavirus’s infection with humans needs to go through the pathway of ACE2 receptor. The similarity between the ACE2 receptor of China Jutous Bat and the human ACE2 receptor is consistent with the potential intermediate host other than other non-human primates. This shows that novel coronavirus, from bat virus to human infection, may not need an intermediate host, but can directly infect humans from bats.

　　In China, the hibernation period of bats is from December to late February. At first, people thought that the virus began to spread at the end of December last year, so the possibility of direct transmission from bats to people was ruled out. However, with more and more retrospective case studies, people found that novel coronavirus had been passed on to people as early as last November. Then, it is possible to pass it directly from bats to people.

　　For example, in a paper published on the website of ChinaXiv on February 21st, researchers from Xishuangbanna Tropical Botanical Garden of China Academy of Sciences, South China Agricultural University and Beijing Brain Center excavated the source and transmission path of Covid-19 from genome data. The researchers collected 93 genome data of novel coronavirus from 12 countries in 4 continents. According to the genome calculation, Covid-19 has undergone two large-scale expansions, one of which was on December 8, 2019.

　　It is inferred that the virus began to spread from person to person at least in early December 2019 or even in late November. Obviously, the virus should be transmitted from animals to people before human transmission. In other words, Covid-19 will be transmitted from animal hosts to humans no later than November 2019.

　　Pangolin may be the intermediate host of Covid-19.

　　At present, the academic circles still accept the conclusion that Covid-19 originated from bats and bats are its natural hosts, but there is no conclusion as to whether Covid-19 directly passed from bats to humans.

　　Many of the early cases of Covid-19 were related to the South China Seafood Market in Wuhan, Hubei Province, where there were a lot of wildlife transactions. China Center for Disease Control and Prevention also reported that Covid-19 was detected in environmental samples obtained from this market. More than 10 years ago, a similar wildlife market has been proved to be related to the SARS outbreak in 2002-2003, so wild animals probably participated in the spread of Covid-19.

　　At present, many scientists are looking for intermediate hosts in Covid-19, among which pangolin is the most likely candidate animal for intermediate hosts in Covid-19.

　　Among the papers speculating that pangolin is an intermediate host, two papers are most worthy of attention at present.

　　On February 18th, Professor Guan Yi from the School of Medicine of Hong Kong University and Hu Yanling from Guangxi Medical University published a paper on bioRxiv, a pre-printed website of medical papers, saying that genome sequencing showed that coronavirus was found in Malay pangolins smuggled from Southeast Asia intercepted in Guangdong and Guangxi, and the similarity with Covid-19 was between 85.5% and 92.4%. The paper holds that the coronavirus pedigrees found in pangolin are very similar to those in Covid-19, and pangolin should be regarded as a possible intermediate host in Covid-19, and it should be forbidden to be sold in fresh markets to prevent the spread of zoonotic diseases.

　　It was South China Agricultural University that first proposed that Malayan pangolin was an intermediate host. On February 7th, South China Agricultural University announced this research result: Pangolin is a potential intermediate host in novel coronavirus. Researchers from South China Agricultural University, such as Shen Yongyi and Xiao Lihua, joined hands with Yang Ruifu, a researcher from the Academy of Military Medicine, and Chen Wu, a senior veterinarian from the Scientific Research Department of Guangzhou Zoo to tackle the problem. By analyzing the virus genome, they found that the virus strain isolated from pangolin was 99% similar to the virus strain currently infecting people, and the receptor binding domains of the two viruses were similar.

　　In the preprint of the paper published later, they claimed that pangolin coronavirus was highly related to Covid-19. In particular, the receptor binding domain of pangolin coronavirus S protein is almost the same as that of novel coronavirus in 2019, with only one amino acid difference.

　　The paper also puts forward important serological evidence, that is, the coronavirus antibody in pangolin’s peripheral blood can bind to Covid-19. Moreover, pangolin infected by virus shows pathological changes and clinical symptoms similar to those of human beings.

　　In this paper, the author also boldly infers that the comparison of existing genomes shows that novel coronavirus in 2019 may have originated from the recombination of pangolin coronavirus and bat coronavirus RaTG13.

　　The paper also said that if the wildlife trade is not effectively controlled, the newly discovered coronavirus may pose a continuous threat to public health.

　　Wild animals are virus reservoirs.

　　What changes did novel coronavirus go through before it was brought into Wuhan and broke out in the crowd?

　　According to the evidence that scientists are looking for now, it may have originated from bats and spread directly to humans; It may also originate from the recombination of bat coronavirus and pangolin coronavirus, and then spread to humans through pangolin.

　　But to be sure, this is not the first or the last virus transmitted from animals to humans. In just 20 years of this century, there have been three kinds of new coronavirus epidemics: SARS, MERS and novel coronavirus.

　　In fact, it is not only the SARS virus and Covid-19 that have caused great losses to our country that are closely related to wildlife. Wild animals are the natural hosts of many serious emerging diseases. Statistics show that at present, 70% of new infectious diseases come from wild animals.

　　For example, natural reservoir, a bat that attracts much attention, has more than 100 kinds of viruses. They can carry many deadly viruses that are very dangerous to people, such as Ebola virus, Marburg virus, SARS virus, MERS coronavirus, Hendra virus and Nipah virus, but they don’t get sick themselves. This may be related to bat’s unique "all-weather" immune system.

　　"We all live on the virus planet, and wild animals are the reservoirs of these viruses." Nathan Wolf, Ph.D. in immunology and infectious diseases at Harvard University, once said this in "The Virus Attacks: How to Deal with the Outbreak of the Next Epidemic".

　　In our country, people have the backward concept of "eat what you eat to make up for what you eat", and there is also the mentality of eating novelty. All kinds of game are served on the table, and all kinds of wildlife trade are repeatedly banned. These invisible dangerous viruses will mutate in various trading links of wild animals and break through the species barrier — — From animal infectious diseases to human infectious diseases. With the increase of population density, the continuous progress of urbanization and the continuous improvement of the convenience of the national transportation network, once the relevant epidemic situation occurs, it will easily turn into a huge disaster and cause huge losses.

　　Although the relevant law enforcement agencies in China have made a series of achievements in prohibiting illegal hunting, breeding, transportation, trading and smuggling of wild animals, due to the lack of ideas and weak market supervision, there are still chaos such as openly selling wild animals and their products, and illegal hunting, transportation and trading of wild animals for the purpose of eating. However, the current Criminal Law and the Wildlife Protection Law lack or are insufficient in provisions on the consumption of wild animals, and the scope and intensity of sanctions are very limited.

　　We expect that, after the passage of the relevant bills banning the consumption of wild animals in an all-round way and severely cracking down on illegal wildlife trading, we will strengthen law enforcement in order to safeguard public health safety and ecological safety legally and in compliance, and prevent the recurrence of epidemics such as SARS and novel coronavirus.

　　Respecting nature, adapting to nature and protecting nature, and making "protecting wild animals and guarding against cross-species transmission of viruses" become the idea of each of us, which is the lesson we should learn from this novel coronavirus epidemic.