Scientists link origins of Covid-19 pandemic to raccoon dogs at Wuhan market

The origin of the Covid-19 pandemic has been the subject of studies over the past three years by the scientific community and the World Health Organization (WHO).

Among the hypotheses of how the coronavirus came to infect humans are direct transmission from animals to humans, the introduction of the virus through an intermediate host, in the food chain or through a laboratory incident.

Theories that seek to explain the origins of SARS-CoV-2 have gained a new element. An international group of researchers claim that genetic data indicate that the onset of the pandemic may be associated with raccoon dogs sold on the market in Wuhan, China.

Context

The emergence of SARS-CoV-2 was first observed when cases of pneumonia of unknown cause were detected in the city of Wuhan, China.

During the first few weeks of the epidemic in Wuhan, an association was observed between the first cases and the Wuhan Seafood Wholesale Market “Huanan”. Cases were mainly reported in local workers and vendors. Authorities closed the market on January 1, 2020 for environmental sanitation and disinfection.

The market, which predominantly sold aquatic and seafood products, as well as some farmed wild animal items, was initially suspected to be the epicenter of the epidemic, suggesting an event at the human-animal interface. Retrospective investigations identified additional cases with disease onset in December 2019, and not all early cases reported an association with Huanan Market.

Human behavior, such as the invasion and destruction of the species’ natural habitats, consumption of wild animals, lack of hygiene protocols and climate change are among the main factors that favor the emergence of outbreaks, epidemics and, ultimately, of a pandemic.

Proximity to preservation areas allows contact with disease-causing agents that, until then, had not infected humans. In this context, there is a phenomenon known technically as spillover – or overflow in free translation, which refers to the adaptation of a microorganism, such as a virus, to go from one host to another.

discoveries

A new analysis of genetic sequences collected from the Chinese market shows that raccoon dogs sold illegally locally may be carrying and possibly spreading the virus since late 2019. The recent findings were reported by the Atlantic magazine. For experts, the pandemic could have a natural origin, and not a laboratory leak, when the coronavirus adapted, passing from animals to humans.

According to the article published in the Atlantic, the study had as its starting point genetic sequences of samples collected in the region of market stalls in Wuhan at the beginning of the pandemic. The first raw data made available to researchers outside of China were published in the international Gisaid database by experts affiliated with the China Center for Disease Control and Prevention. Scientists from Europe, North America and Australia identified the sequences and began an analysis.

The study led by Kristian Andersen, Edward Holmes and Michael Worobey points out that the samples identified in the market region contained animal genetic material, including content compatible with that of the raccoon dog.

Considering the characteristics of the viruses, which do not remain isolated in the environment, the scientists hypothesized that raccoon dogs could have been infected by the coronavirus in the market area. However, according to the researchers, the identification of the genetic material of the virus and the closely mixed mammal is just an indication of animal participation in the epidemiological context of the emergence of the pandemic.