Did snakes transmit the deadly new Coronavirus to humans? Scientists doubt

As scientists across the world continue to grapple with the origin of the deadly new strain of coronavirus in China, which has infected over 2,000 people across countries, a research team in Beijing has found that snakes are the reservoirs of the deadly virus. Several virologists, however, remain skeptical about the new finding.

Finding the reservoir and the host is crucial, for it could help scientists to gauge the actual threat of how virulent the strain is and if the outbreak has the potential to persist and accordingly prepare for the crisis. Genetic information of the “animal” could help in determining the extent of human-to-human transmission.

The study published recently in the Journal of Medical Virology was carried out by a team of microbiologists from Peking University Health Science Center, School of Basic Medical Sciences, Beijing.

According to the team, two snakes- Bungarus multicinctus (the many-banded krait) and Naja atra (the Chinese cobra), which are commonly sold at the Wuhan seafood and animal market could be the most likely animal reservoir for the 2019-nCoV.

The link was established on the basis of “codons”, which are basically sequences of three nucleotides in DNA or RNA that encode amino acids –the building blocks of proteins. Sometimes, viruses tend to encode proteins, using the same choice of codons as their host to adapt themselves to it.

In this case, they compared the codons favoured by the virus to hedgehogs, a spiny mammal, pangolins (anteaters), chickens, bats, humans and snakes, but found them to be most similar to those used by the two snakes.

The new findings, have however, raised many questions as stated in the article published in the peer-reviewed journal, Nature, according to which there is no concrete evidence till date, that supports, that these viruses can infect any other species other than mammals and birds.

“Nothing supports snakes being involved,” said David Robertson, a virologist at the University of Glasgow, UK, who said, that it is unlikely that 2019-nCoV has infected any secondary animal host for long enough to change its genome significantly. “It takes a long time for such a process to play out,” he added.

Another virologist, Paulo Eduardo Brandao, from University of Sao Paulo, told Nature that there was no consistent evidence that coronaviruses can infect snakes at all, or "have hosts other than mammals and Aves (birds)."

Scientists suspect that an unknown animal carrying 2019-nCoV transmitted the virus to humans at a live seafood and wild animal market in Wuhan, where the first cases were documented in late December. In case of the SARS outbreak in 2002, civets were believed to have transmitted the virus to humans from bats.

"The initial cases of current outbreak were epidemiologically linked to Sea food market in Wuhan, China, which has several animals for sale. Early analysis of the genome also indicated that SARS CoV and nCoV 2019 share the same receptor for attachment to host cell," said Prof. G Arunkumar, Director, Manipal Institute of Virology.

Both SARS CoV and 2019-nCoV belong to the family of Coronaviruses and are part of the same virus subgroup known as beta-coronaviruses.

"Clearly this 2019-nCoV is a mammalian virus," said Cui Jie, a virologist at the Pasteur Institute of Shanghai, who was part of the research team that identified the single population of horseshoe bats that harboured virus strains of SARS virus which jumped to humans in 2002, killing almost 800 people around the world.

Bats have long been known to be reservoirs of such coronaviruses. However, more field and laboratory work is needed to establish any links.

Researchers hope that genetic tests of samples collected from cages and containers from the Wuhan sea food market could offer some clues. The sea-food market is also known to sell wide range of wild animals along with bats and poultry.