Corona virus: Missing links to animal-to-human transmission may never be found

Corona virus: Missing links to animal-to-human transmission may never be found

Evidence suggests that the corona virus was transmitted from bats to humans through an 'intermediate host' animal.

Although the World Health Organization says research points to the natural origin of the virus, some scientists say it may never be known how it first infected humans.

It is not clear if the host animal was sold at the Wuhan Wildlife Market. But the wildlife business is being seen as a possible source of the epidemic.

Researchers say that this business is a means of transmitting diseases among different species, which has spread the previous epidemics and is also being held responsible for this global epidemic.

"We were preparing for a similar situation because the problem was not if, but when," Maria Van Karkhov, head of research at the World Health Organization, told the BBC.

Image captionThe virus originated in bats and was transmitted to humans through an intermediate host

Transmission between different types of viruses

Infectious disease experts agree that the virus, like other human diseases, has crossed the barrier between species without being seen.

"We were really looking forward to it," says Andrew Cunningham, a professor at the Zoological Society of London.

"These diseases have become more prevalent in recent years due to increasing human encroachment on wildlife habitats, exposure to them and increased use of wild animals."

This is not the first case of the virus being transmitted from one organism to another.

Rather, it is a new addition to Ebola, H5N1, SARS and MERS. These diseases were first detected in wild bats. The strongest evidence of this came during research into the 2003 SARS epidemic.

Somewhere in 2017, scientists went to a cave in China and discovered a 'treasure trove of stork bats' genes.'

To transfer to a new host, the virus needs the ability to break the locks of its target cells. In stork-like bats, the ancestor of the coronavirus had the human cell key.

Professor David Robertson, a virologist at the University of Glasgow, explains: 'In the case of Sars-CoV-2, the key is a virus protein or protein called a spike and a large lock to enter the cell called ACE2.

"Corona virus not only fits perfectly in ACE II, but also performs much better than SARS-1."

Its ability to fit perfectly explains how it is so easily transmitted from one person to another and why all our efforts to stop it are not working. But wildlife plays a key role in bringing the bat virus to the doorsteps of human cells.

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Image captionChina seizes Musk call or cats from Shenyang's wildlife market to stem SARS epidemic

Buying and selling and getting sick

Most of us have heard that the virus originated from a wildlife market in Wuhan. But the root of the virus, the animal in which it was born, could not be identified.

James Wood, a professor at the University of Cambridge, said: "Initially, the virus was found in people who belonged to this market, but this is factual evidence.

"The infection may have come from somewhere else and it's just a coincidence that it has affected so many people in one place. But being an animal virus, its connection to this market reveals a significant clue.

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Image captionCoronavirus image from a microscope

Professor Cunningham seems to agree because, according to him, wildlife markets are the breeding grounds for animal diseases where new hosts are found.

He says: 'The combination of many species in poor hygiene conditions, even the proximity of species that do not normally come into contact with each other, provides ample opportunities for germs to be transmitted from one species to another. does.'

In the past, many of these viruses have been transmitted to humans from other species, species that are either farmed or sold in hunting markets.

Professor Wood says that the stork was first transmitted to humans by the palm musk bale, which was sold for food in southern China.

Image copyrightVICTORIA GILL

Image caption Capturedforeign pets have to be protected from human diseases

"It's important to know that palm musk was also a pandemic at the time, and it was important to stop the pandemic in these animals to prevent the transmission of the disease to humans."

In search of the missing link, scientists have found some important clues in aquatic neoplasms, white nebulae, and even turtles.

Similar viruses have been found in the bodies of rare and smuggled pangolins. But there is no doubt about the nature of the recent epidemic. However, it is clear that wildlife trade and contact with them is dangerous for both humans and these animals.

"It's important to keep wild animals away from yourself or your pets," said Professor Wood.

But regulating the wildlife trade is a complex process.

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Image captionCamels can breed coronaviruses that cause measles

According to Professor Wood, there have been several attempts to curb the wildlife trade and its access to it. But what happens is that only a few poor people fall victim to them. "After enforcing such rules many times, the business goes underground and then you can't do anything about it."

The World Health Organization (WHO) has called for stricter standards for hygiene and protection in China's wildlife markets. But often such businesses are run informally, making it difficult to regulate.

Professor Wood says: "You can't implement them sitting in London or Geneva, you have to work locally in every country."

It will be a universal but complex task. But Covid-19 has proven that the cost of not doing so is very high.