Snakes may be the original source of the new coronavirus outbreak in China

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The multi-band krait (Bungarus multicinctus), also known as Taiwan krait or Chinese krait, is a highly poisonous species of elapid snake found in much of central and southern China and in Southeast Asia.

The disease was first reported in late December 2019 in Wuhan, a large city in central China, and is spreading rapidly. Since then, sick travelers from Wuhan have infected people in China and other countries, including the United States.

Using samples of the virus isolated from patients, scientists in China determined the virus's genetic code and used microscopes to photograph it. The pathogen responsible for this pandemic is a new coronavirus. It is in the same family of viruses as the well-known severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle Eastern respiratory syndrome coronavirus (MERS-CoV), which have killed hundreds of people in the past 17 years. The World Health Organization (WHO) has named the new coronavirus 2019-nCoV.

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We are virologists and journal editors and they are following this outbreak closely, because there are many questions that need to be answered to contain the spread of this threat to public health.

What is a coronavirus?

The name of the coronavirus comes from its shape, which resembles a solar crown or crown when photographed using an electron microscope.

A visual guide to the Wuhan coronavirus

The electron microscopic image reveals the structural details of the crown shape for which the coronavirus was named. This image is of the Middle Eastern respiratory syndrome coronavirus (MERS-CoV). National Institute of Allergy and Infectious Diseases (NIAID)

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Coronavirus is transmitted through the air and mainly infects the upper respiratory and gastrointestinal tracts of mammals and birds. Although most members of the coronavirus family cause only mild flu symptoms during infection, SARS-CoV and MERS-CoV can infect the upper and lower airways and cause severe respiratory disease and other complications in humans.

This new 2019-nCoV causes symptoms similar to those of SARS-CoV and MERS-CoV. People infected with these coronaviruses experience a severe inflammatory response.

Unfortunately, there is no vaccine approved or antiviral treatment available for coronavirus infection. A better understanding of the 2019-nCoV life cycle is needed, including the source of the virus, how it is transmitted and how it replicates to prevent and treat the disease.

Zoonotic transmission

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Both SARS and MERS are classified as zoonotic viral diseases, which means that the first infected patients acquired these viruses directly from animals. This was possible because, while hosted on the animal, the virus had acquired a series of genetic mutations that allowed it to infect and multiply within humans.

First American case of Wuhan coronavirus confirmed by CDC
These viruses can now be spread from person to person. Field studies have revealed that the original source of SARS-CoV and MERS-CoV is the rod and that the masked palm civets (mammal native to Asia and Africa) and camels, respectively, served as intermediate hosts between bats and humans.

In the case of this coronavirus outbreak in 2019, reports state that the majority of the first group of hospitalized patients were workers or customers in a local wholesale seafood market, which also sold processed meats and live consumables, including poultry, donkeys, sheep, pigs, camels, foxes, badgers, bamboo rats, hedgehogs and reptiles. However, as no one has ever reported finding a coronavirus infecting aquatic animals, it is plausible that the coronavirus may have originated from other animals sold on this market.

Life at ground zero of the Wuhan coronavirus outbreak
The hypothesis that 2019-nCoV jumped from an animal on the market is strongly supported by a new publication in the Journal of Medical Virology. The scientists conducted an analysis and compared the 2019-nCoV genetic sequences and all other known coronaviruses.

The 2019-nCoV genetic code study reveals that the new virus is more closely related to two SARS-like coronavirus samples from China, initially suggesting that, like SARS and MERS, the bat may also be the source of 2019-nCoV. The authors also found that the viral RNA coding sequence for the spike 2019-nCoV protein, which forms the "crown" of the virus particle that recognizes the receptor in a host cell, indicates that the bat virus may have mutated before to infect people.

But when the researchers performed a more detailed bioinformatics analysis of the 2019-nCoV sequence, it suggests that this coronavirus may come from snakes.

Wuhan Huanan's wholesale seafood market, where the coronavirus outbreak is believed to have started, is now closed.

From bats to snakes

The researchers used an analysis of the protein codes favored by the new coronavirus and compared it with the protein codes of the coronaviruses found in different animal hosts, such as birds, snakes, marmots, hedgehogs, manis, bats and humans. Surprisingly, they found that the protein codes in 2019-nCoV are more similar to those used in snakes.

Snakes often hunt bats in the wild. Reports indicate that the snakes were sold at the local seafood market in Wuhan, increasing the possibility that 2019-nCoV jumped from the host species – bats – to snakes and then to humans at the beginning of this coronavirus outbreak. However, how the virus can adapt to cold-blooded and warm-blooded hosts remains a mystery.

The report authors and other researchers must verify the origin of the virus through laboratory experiments. Looking for the 2019-nCoV sequence in snakes would be the first thing to do. However, since the outbreak, the seafood market has been disinfected and closed, making it difficult to trace the animal of origin of the new virus.

Sampling of viral RNA from animals sold on the market and from wild snakes and bats is necessary to confirm the origin of the virus. However, the reported findings will also provide information for the development of prevention and treatment protocols.

The 2019-nCoV outbreak is another reminder that people should limit wildlife consumption to prevent zoonotic infections.
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