the mystery of its animal origins thickens

While the Covid-19 epidemic is present on all continents, scientists are still looking for the species that causes human transmission of the Sars-CoV-2 coronavirus. An investigation essential to understand the emergence of the disease but in which the evidence is not yet conclusive.

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The 3 March 2020, theepidemic de Covid-19 has crossed the bar of the 90,000 infected worldwide. While the number of new daily cases has never been so low in China, the cradle of the epidemic, other countries are seeing the disease spread like wildfire. Faced with this new disease, which no longer spares any inhabited continent, scientists are hard at work to understand the coronavirus Sars-CoV-2, the etiological agent from Covid-19. And the question of its origin is far from being resolved.

Bats, snakes, pangolins, several animal species transiting through the market in Wuhan, the starting point of the epidemic, have been implicated, as a natural reservoir or host intermediate coronavirus, by researchers.

But each publication posted on Biorvix was accompanied by a following questioning it. As a reminder, the site Biorvix is a prepublication site, the referenced works have not followed the classic scientific publication path, namely a peer review where methodological or interpretation errors are raised and then revised by the authors. A long process, but one that enhances the value of the published results. On the other hand, pre-publication, although having its limits, is very useful for communicating scientific results quickly in a situation that evolves as quickly as an epidemic.

The SARS-CoV-2 coronavirus intermediate host in question

In early February, Chinese researchers claimed that the Sars-CoV-2 and a pangolin-isolated coronavirus shared 99% of their genome. A communication error since their study, posted on February 20 on Biorvix, reveals that it is in reality only ” receptor-binding domain “(Receptor binding domain) of the protein of surface S and which presents only one amino acid of difference with the protein S domain of the Sars-CoV-2 coronavirus. We are therefore far from match genetic 99% in between virus.

Two other studies, published the same day, suggest that the virus responsible for Covid-19 shares, for one, 90.23% and, for the other, 91.02% of its genome with the strains isolated from the pangolins tested. This similarity is not enough to make pangolin a host for the virus.

In the case of the Sars epidemic of 2002-2003, the Sars-CoV shared 99.8% of its genome with a coronavirus isolated from civets, making this small mammal congratulates the intermediate host of the virus and the link between its natural reservoir and humans.

The bat, a serious track in the emergence of the epidemic

The bats are still considered the most likely source of Sars-CoV-2. A coronavirus isolated from the flying mammal is genetically closest to the virus circulating between humans, 96% of the genetic material is common. Could the virus have passed from the bat to humans without an intermediate host?

The differences between the famous “ receptor-binding domain Of the two viruses suggests that the bat coronavirus could not infect humans without an intermediate host, the researchers said.

But who is this intermediate host that escapes scientists? The publications on the subject raise more questions than they solve. The investigation still promises to be long.

Coronavirus: pangolin suspected of being the missing link

Article published on February 7, 2020 by Futura with AFP-Relaxnews

The pangolin is thespecies the most poached in the world, far ahead of elephants or rhinoceros. Victim of illegal trafficking, this small mammal, threatened withextinction, is highly prized for its flesh, scales, bones and organs in the traditional medicine Asian. It could be the animal that transmitted the virus, this is what Chinese researchers say while others call for caution.

Is the pangolin, a small mammal with scales threatened with extinction, the animal that transmitted the new coronavirus to humans? Chinese researchers advanced the hypothesis on Friday, but other scientists are cautious while awaiting final confirmation.

The animal, which hosts a virus without being sick and can transmit it to other species, is called “reservoir”. In the case of the new coronavirus, it is certainly a bat: according to a recent study, the genomes of this virus and of those which circulate in this animal are identical to 96%. But the virus bat not being equipped to fix itself on the human receptors, it undoubtedly passed by another species to adapt to the man.

Is the pangolin the missing link?

The identity of this intermediate animal has been the subject of many questions since the beginning of the epidemic. The snake hypothesis was soon swept aside. Friday the University ofAgriculture from southern China ruled that the pangolin could be ” a possible intermediate host Without however giving much details. We only know that genetic analyzes of viruses taken from pangolins and the Men were 99% identical, according to the new Chinese state agency. These elements are ” not enough to conclude, tempered a British scientist, Professor James Wood. Evidence for pangolin involvement has not been published in a scientific journal “, An essential criterion to accredit this hypothesis, he commented.

” We would have to see all the genetic data to know the degree of proximity between the pangolin and human viruses “Added another British scientist, Professor Jonathan Ball. The new virus appeared in December in a market of Wuhan (central China). Despite its name as a Seafood Market, many other animals, including wild mammals, were sold there for food. It is not known if the pangolin was one of them. During the’SARS epidemic (2002-2003), also caused by a coronavirus, the intermediary was the civet, a small mammal whose meat is appreciated in China.

How are animal surveys carried out?

Before targeting the pangolin, Chinese researchers tested more than 1,000 samples from wild animals. They must have identified all the types of animals sold in the market and tested to see if they were carriers of the drug. virus. For that, we realize ” pharyngeal swab (in the throat, note) and a stool sample “, Explains to AFP Arnaud Fontanet, of the Pasteur Institute.

Virologist Martine Peeters, fromIRD (Research Institute for Development), investigated in Africa to find the animal reservoir of the Ebola virus. There too, the bat was involved. The researcher describes samples taken from this animal: ” They pass a swab in their mouth and another in the rectum” If you do not have the animal itself, you must also collect excrement from the wild. ” We collected thousands of droppings in many sites in Africa “Says Martine Peeters to AFP.

This is probably also what Chinese researchers did for the new coronavirus, especially as the Wuhan market was closed at the start of the epidemic. At the end of January, a Chinese team said they had taken 585 samples from stalls and a garbage truck from the market, and ” having found the coronavirus in 33 of them, says Professor Fontanet. They don’t say which samples it was, but I think it was excrement lying around on the benches. “

The importance of knowing the animal responsible for the epidemic?

Knowing the animal that transmitted the virus to humans can help prevent the virus from re-appearing once the epidemic has been brought under control. ” It is by prohibiting the consumption of civets and by closing the breeding farms that we had been able to prevent any reintroduction [virus[duvirusduSras in humans, editor’s note]», Reminds Professor Fontanet. If the pangolin hypothesis is confirmed, the quest for the animal responsible for the epidemic caused by the new coronavirus will have been rapid, as for the SARS.

For other illnesses, it can take much longer. ” In the case of Ebola, searches for the reservoir began in 1976 and the first results were published in 2005 “Reminds AFP Eric Leroy, virologist and veterinarian of the IRD. For the AIDS virus, the HIV, the investigation lasted twenty years before pointing to the great apes, notes Martine Peeters.

What threats are now hanging over the pangolin?

Nearly 100,000 pangolins are victims each year in Asia and Africa of a illegal traffic which makes it the most poached species in the world, far ahead of elephants or rhinos, according to the NGO WildAid. Their delicate flesh is highly prized by Chinese and Vietnamese gourmets, as are their scales, their bones and their organs in traditional Asian medicine.

In 2016, the International Convention on Trade in Endangered Species ofextinction (Cites) voted to include pangolins in its appendix 1, which strictly prohibits its trade. Despite this measure, their traffic has only increased, according to NGOs. ” Wild animals-humans are the source of these transmissions, so leave them animals wild where they are “Says Professor Fontanet.

Conclusion of a study published Monday in the medical journal Nature, Chinese researchers have advocated “ the establishment of a strict legislation against the breeding and consumption of animals wild ” A transitional measure has already been taken: at the end of January, China banned the trade in all wild animals pending the end of the epidemic.

“ Each time, we try to put out a fire and, when it is extinguished, we wait for the next “, Regrets François Renaud, a CNRS researcher. According to him, it would be necessary to “map everything that is potentially liable to transmit infectious agents to humans”, while conceding however that this “inventory of risks” on a global scale would represent a huge work and would require significant funding. .

Bats are the reservoir of the new virus from China

Article by Julie Kern, published on January 26, 2020

Scientists are struggling to better characterize 2019-nCoV, a new strain of coronavirus that is shaking China. A first hypothesis on its reservoir was put forward a few days ago, here is a second one which favors bats. And which also brings 2019-nCoV closer to the SARS agent.

As the days go by, the 2019-nCoV coronavirus reveals its secrets a little more. In an article published yesterday, we discussed the reservoir of the virus: snakes sold on the Wuhan market, according to the first elements gathered by researchers from the Beijing Medical University. The scientists behind this study suggest that 2019-nCoV is derived from a recombination between two coronary arteries, one of which is specific to bats.

A new study, prepublished in bioRvix, conducted by researchers from the Chinese Academy of Sciences, seems to confirm the relationship between bats and 2019-nCoV. In addition, it would belong to the same species as SARS-CoV, the agent responsible for an epidemic of pneumonia deadly 18 years ago.

2019-nCoV is close to SARS-CoV

The work of sequencing genomics was made from viruses isolated from five different patients at an early stage of the disease. By entire comparison of the genome, it appears that 2019-nCoV and a viral strain of bats are 96% identical.

Another new development, 2019-nCoV would also be a close cousin of SARS-CoV, whose reservoir is the bat. These two viruses share 79.5% of their genome, but also the same protein, ACE2, which they use door of entry into the cells of the mucosa respiratory.

Should we therefore abandon the snake hypothesis? If the natural reservoir of 2019-nCoV seems rather to be bats, the snakes described above could be the intermediate host between bats and humans. In the case of SARS-CoV, humans were infected during close contact with masked palm civets (Paguma larvata), also sold and consumed in Chinese markets. Of course, this is only an assumption.

Viruses in China: are snakes the cause of the epidemic?

Article published on January 23, 2020 by Julie Kern

As China steps up health measures to limit the spread of 2019-nCoV, which has already killed 17 people, scientists seem to have pinpointed the animal reservoir for this new coronavirus.

The epidemic of pneumonia caused by a new coronavirus in China continues to expand. This January 23, there are 555 confirmed cases, mainly in Hubei province where Wuhan is located, and 17 people who died. The epidemic is concentrated in eastern China and to surrounding countries although a first case has been identified in Seattle in the United States.

The Chinese government has instituted drastic measures to contain the spread of 2019-nCoV. Wuhan airports and train stations are closed, cutting the city off from the rest of the world. The World Health Organization (WHO) prolonged its meeting due to the lack of information communicated by China. ” The decision whether or not to declare a public health emergency of international concern is a decision that I take very seriously and that I am only prepared to take with due consideration of the available evidence. “Said WHO director Tedros Adhanom Ghebreyesus in Geneva, Switzerland, to the press.

For their part, scientists are continuing their investigations to better understand this previously unseen strain. A research team from the Beijing Medical University published a study on January 22 Journal of Medical Virology. These researchers believe they have identified the origin of this epidemic which worries the whole world: snakes.

2019-nCoV, resulting from a recombination, would come from snakes

Coronaviruses are rather common in mammals and birds, especially in species close to humans such as pigs, cats, rats or poultry. To trace the origin of the virus, Chinese scientists compared more than 200 genomes of animal-infected coronaviruses with that of 2019-nCoV. By comparing the genetic sequences which are specific to the host of the virus by bioinformatics, it appears that snakes would be the most probable reservoir among all the species studied.

In addition, the genome of the Wuhan coronavirus was born from the recombination of two coronaviruses: one known to infect bats and the other with unknown origins. Some of these proteins therefore differ from those of its “parents”. This is the case of a glycoprotein which authorizes the entry of the virus into other cells. This change would have allowed 2019-nCoV to cross the species barrier to infect humans.

2019-nCoV, an emerging zoonosis

The track of the zoonosis was favored by scientists because the epidemic broke out in a Wuhan food market. As a reminder, a zoonosis is a viral, bacterial or parasitic animal disease, capable of infecting humans following a mutation. But what is the relationship between snakes and a market in Pisces ? According to the authors, snakes are commonly found for sale on the stalls of this market, especially the species Bungarus multicinctus and Naja atra who live in the area.

It is the first study to identify a potential reservoir for Wuhan coronavirus. Other species, also abundant at the Wuhan market, will also be investigated.