We all remember the pangolin. The small, scaled, snout-faced mammal that was propelled onto the front page of all major news media, incriminated in the spread of one of the most dramatic and deadly episodes of the 21st century. It has since been exonerated. Pangolins are not the original carrier of the SARS-CoV-2 virus, the virus responsible for the COVID-19 pandemic. But the hunt for the origin of the COVID-19 pandemic has new leads, as a new study published last month identifies new potential hosts.
The paper reveals the half a dozen animal species that could have served as intermediate hosts for SARS-CoV-2, the coronavirus that causes COVID-19, and passed the virus to people. Based on genetic sequences of samples collected at the time, these species were present at the end of 2019 at the likely epicentre of the pandemic, the Huanan market in Wuhan,China. Thanks to genetic sequencing of samples taken from the market stalls after the market closed in January 2020, scientists highlighted the co-presence of genetic material from SARS-CoV-2 and certain wild animals. Among the species identified were raccoon dogs and civets, two species already implicated in the emergence of SARS in 2002 and thought to have contributed to the passing of the SARS virus to humans.
Raccoon dogs are wild canids related to foxes with markings similar to raccoons, and civets are small carnivorous mammals related to mongooses and hyenas. Traces of the bamboo rat and the Malayan porcupine have also been found in SARS-CoV-2 positive samples. Analysing in detail the genetic particularities, and comparing them to databases, researchers were able to tell where the animals present on the market came from. For instance, the raccoon dogs are thought to have come from southern or central China, not northern China, where fur farms are usually located.
At the same time, the scientists studied the viral genomes of the first patients with Covid-19 in order to trace the possible evolution of the virus. They highlighted that the genetic diversity of the virus present in the market was representative of the genetic diversity of the early human cases of the pandemic. This supports the theory that the pandemic originated in that overcrowded Chinese market and that the virus was introduced by infected animals into the market in late 2019.
Researchers also revealed the presence of other zoonotic viruses in the market, highlighting the high risk of interspecies infection with pandemic potential, linked to the sale of live animals in densely populated cities. Identifying the human activities most likely to trigger new pandemics is crucial to better anticipate and prevent these major events. This type of information could help guide and inform surveillance strategies to ensure we don’t get taken by surprise by an outbreak in animals, which could pose a threat not just to animal health but to human health as well. Indeed, 60% of known infectious diseases in people can be spread from animals. The Covid-19 pandemic is only one example among others that shows that it is important to control pathogens in animal populations.
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Last edited: 31 October 2024 12:43