The mysteries surrounding the origins of Covid-19 continue to intrigue scientists. A recent study reveals new information about the Wuhan market, which has been under scrutiny since the beginning.
The animal species present in this market at the end of 2019 could be the key. Genetic data reveals a troubling connection with the Covid-19 virus. And it's no longer necessarily the pangolin that's in the spotlight.
Image Wikimedia
Samples were taken after the Wuhan market's closure. The results show a co-presence of SARS-CoV-2 genetic material and that of certain wild species, such as raccoon dogs and civets. These animals have been associated with similar outbreaks in the past.
These discoveries are based on genetic sequencing, allowing analysis of organisms present in each sample. This method, called meta-transcriptomics, has also identified other zoonotic viruses in the market, increasing concerns about future pandemics.
The raccoon dog, in particular, could play a role in transmitting the virus to humans. Tests confirmed that this animal, present in Wuhan's stalls, was carrying the virus.
Researchers also analyzed the first viral genomes of Covid-19 patients. The results show genetic diversity similar between the market samples and early human cases.
This study reinforces the hypothesis that the Wuhan market may have been the starting point of the pandemic. It also underscores the urgency of regulating the trade of live animals to prevent potential health crises.
Densely populated urban markets where wild animals are sold pose a high risk. Scientists are calling for surveillance to prevent new global catastrophes.
What is a zoonosis and why is it important for understanding pandemics?
A zoonosis is an infectious disease that can be transmitted from animals to humans. These infections are caused by pathogens (viruses, bacteria, parasites) that are hosted by animal species and, at times, cross the species barrier to infect humans.
Zoonoses play a crucial role in the emergence of pandemics. SARS-CoV-2, responsible for Covid-19, is a striking example, with evidence suggesting that the virus passed from wild animals, through an intermediate host, to humans. Monitoring interactions between animals and humans is thus essential to prevent future outbreaks.
Certain species, such as bats, naturally harbor many viruses. These natural reservoirs, when they interact with intermediate animals or humans under specific conditions, increase the risk of transmission. The sale of wild animals in dense urban markets, such as that of Wuhan, illustrates this high risk of spread.
How does the "meta-transcriptomic" technique help identify viruses in a market?
Meta-transcriptomics is a genetic analysis technique that allows the sequencing of RNA from all organisms present in a sample. This includes viruses, bacteria, animals, plants, and even humans. It is used to precisely identify the species present in a given environment.
In the study on the Wuhan market, this method enabled researchers to analyze samples collected from the stalls. By sequencing RNA, they were able to detect the presence of SARS-CoV-2 genetic material, as well as that of various animals, suggesting a co-existence between these viruses and certain animal species.
Meta-transcriptomics is therefore a powerful tool to understand species interactions and identify pathogens in real time, without the need for specific cultures. This technique allows for rapid and accurate analysis of complex environments like markets where wild animals are sold.
Why is the raccoon dog a key suspect in the origin of Covid-19?
The raccoon dog is a wild species often sold in Chinese markets, including the Wuhan market. It is known to be a potential carrier of viruses like SARS-CoV-2, as it can be infected by the virus and transmit it to other animals or humans.
Samples collected from the Wuhan market revealed the presence of raccoon dog DNA, co-existing with genetic material from SARS-CoV-2. These clues suggest that this animal could have served as an intermediate host, facilitating the transmission of the virus from bats to humans.
Due to this ability to harbor and transmit the virus, the raccoon dog is considered a central player in the emergence of Covid-19. Its potential role highlights the importance of monitoring interactions between humans and wildlife in markets.