Estudios científicos concluyen que pandemia de covid comenzó en mercado de Wuhan/Wuhan market was epicentre of pandemic’s start, studies suggest

Los investigadores dijeron no haber encontrado apoyo para una hipótesis alternativa de que el coronavirus escapó de un laboratorio en China

Dos estudios científicos concluyen que el coronavirus estaba presente en los mamíferos vivos que vendían en el mercado mayorista de mariscos de la ciudad de Wuhan, en China, a finales de 2019 y que se propagó a sus trabajadores. Esto según publica este sábado el New York Times.

Para estos dos estudios, que en conjunto tienen 150 páginas y que aún no han publicado en revistas científicas, analizaron datos de variedad de fuentes para buscar pistas sobre cómo surgió la pandemia, y descarta que haya salido de un laboratorio, agrega el diario.

«La agrupación geográfica de los primeros casos conocidos de covid-19 y la proximidad de muestras ambientales positivas a vendedores de animales vivos sugieren que el mercado mayorista de mariscos de Huanan en Wuhan fue el lugar de origen de la pandemia». Así lo señalan los científicos en el estudio.

Los investigadores dijeron no haber encontrado apoyo para una hipótesis alternativa de que el coronavirus escapó de un laboratorio en Wuhan.

“Cuando observas toda la evidencia en conjunto, es una imagen extraordinariamente clara de que la pandemia comenzó en el mercado de Huanan”, indicó el biólogo evolutivo de la Universidad de Arizona y coautor de ambos estudios.

El Times destaca además que los autores del nuevo estudio incluyen investigadores que publicaron previamente informes más pequeños que apuntaban a una conclusión similar, pero basados ​​en muchos menos detalles.

Pandemia del covid comenzó en Wuhan según estudios científicos
«Comprender las circunstancias que conducen a las pandemias es fundamental para su prevención. Aquí, analizamos el patrón y el origen de la diversidad genómica del SARS-CoV-2 al comienzo de la pandemia de covid-19 «, explican además en una introducción al estudio.

También que la primera transmisión zoonótica ocurrió a fines de noviembre o principios de diciembre de 2019 y no antes de principios de noviembre de 2019.

El diario recuerda que muchos de los primeros casos de la covid-19 se agruparon alrededor del mercado de Wuhan y que a finales de diciembre de 2019, los hospitales de la localidad habían encontrado decenas de casos de neumonía viral.

En enero del año pasado expertos de la Organización Mundial de la Salud que investigaban el origen del virus en China visitaron precisamente ese mercado, donde se detectaron los primeros contagios. El primero fue un hombre que había estado en el mercado, que fue cerrado el 1 de enero del 2020.

Ese mismo día cientos de miles de personas dejaron la ciudad de Wuhan para regresar a sus lugares de origen para el Año Nuevo Lunar, propagando así el virus, destacó además el Times. EFE

Covid-19 comenzó en Wuhan

Wuhan market was epicentre of pandemic’s start, studies suggest

Report authors say that the coronavirus SARS-CoV-2 jumped from animals sold at the market into people twice in late 2019 — but some scientists want more definitive evidence.

Scientists have released three studies that reveal intriguing new clues about how the COVID-19 pandemic started. Two of the reports trace the outbreak back to a massive market that sold live animals, among other goods, in Wuhan, China1,2, and a third suggests that the coronavirus SARS-CoV-2 spilled over from animals — possibly those sold at the market — into humans at least twice in November or December 20193. All three are preprints, and so have not been published in a peer-reviewed journal.

These analyses add weight to original suspicions that the pandemic began at the Huanan Seafood Wholesale Market, which many of the people who were infected earliest with SARS-CoV-2 had visited. The preprints contain genetic analyses of coronavirus samples collected from the market and from people infected in December 2019 and January 2020, as well as geolocation analyses connecting these samples to a section of the market where live animals were sold. Taken together, these different lines of evidence point towards the market as the source of the outbreak — much like animal markets were ground zero for the severe acute respiratory syndrome (SARS) epidemic of 2002–2004 — says Kristian Andersen, a virologist at the Scripps Research Institute in La Jolla, California, and an author on two of the reports. “This is extremely strong evidence,” he says.

Still, none of the studies contain definitive evidence about what type of animal might have harbored the virus before it spread to humans. Andersen speculates that the culprits could be raccoon dogs, a squat dog-like mammal used for food and for their fur in China. One of the studies he coauthored2 suggests that raccoon dogs were sold in a section of the market where several positive samples were collected. And reports4 show that the animals are capable of harboring other types of coronaviruses.

Some virologists say that the new evidence pointing to the Huanan market doesn’t rule out an alternative hypothesis. Namely, they say that the market could have just been the location of a massive amplifying event, in which an infected person spread the virus to many other people, rather than the place of the original spillover.

“Analysis-wise, this is excellent work, but it remains open to interpretation,” says Vincent Munster, a virologist at the Rocky Mountain Laboratories, a division of the National Institutes of Health, in Hamilton, Montana. He says searching for SARS-CoV-2 and antibodies against it in blood samples collected from animals sold at the market, and from people who sold animals at the market, could provide more definitive evidence of COVID-19’s origins. The number of positive samples from the market suggests an animal source, Munster says. But he is frustrated that more thorough investigations haven’t already been conducted: “We are talking about a pandemic that has upended the lives of so many people.”

Ground zero?
In early January 2020, Chinese authorities identified the Huanan market as a potential source of a viral outbreak because the majority of people infected with COVID-19 at that time had been there in the days before they began to show symptoms, or were in contact with people who had. Hoping to stem the outbreak, Chinese authorities shuttered the market. Then researchers collected samples from poultry, snakes, badgers, giant salamanders, Siamese crocodiles and other animals sold there. They also swabbed drains, cages, toilets and vendor stalls in search of the pathogen. Following an investigation led by the World Health Organization (WHO), researchers released a report in March 2021 showing that all of the nearly 200 samples collected directly from animals were negative, but that more than 1,000 environmental samples from the stalls and other areas were positive.

A research team from China including the head of China’s Center for Disease Control and Prevention (CDC) has now genetically sequenced those positive samples, releasing the results in a preprint posted on 25 February1. The scientists confirm that the samples contain SARS-CoV-2 sequences nearly identical to those that have been circulating in humans. Further, they show that the two original virus lineages circulating at the start of the pandemic, called A and B, were both present at the market.

“It’s a nice piece of work,” says Ray Yip, an epidemiologist who is a former director of the China branch of the US Centers for Disease Control and Prevention. “They’ve confirmed that the Huanan market was indeed a very important spreading location.”

As soon as the report from China posted online, Andersen and his colleagues rushed to post the manuscripts they had been working on for weeks.

In one2, the team zeroed in on the southwestern section of the Huanan market, where live animals were sold as recently as 2019, as being the potential epicentre of the outbreak. They arrived at this conclusion by compiling information on the first known COVID-19 cases in China, as reported in various places, including the WHO investigation, newspaper articles, and from audio and video recordings of doctors and patients in Wuhan. This geospatial analysis found that 156 cases in December 2019 clustered tightly around the market and then gradually became more dispersed around Wuhan in January and February 2020.

They also examined the locations of the positive samples collected in the market, as reported in the WHO study, and fleshed out information about their potential surroundings by collecting business registration information, photographs of the market before it closed, and scientific reports that have emerged since the WHO’s investigation. For example, one paper published last year5 documented some 47,000 animals — including 31 protected species — sold in Wuhan markets between 2017 and 2019.

In one major finding in the new preprint, Andersen and colleagues mapped five positive samples from the market to a single stall that sold live animals, and more specifically to a metal cage, to carts used to move animals, and to a machine used to remove bird feathers. One of the coauthors on the report, virologist Eddie Holmes at the University of Sydney in Australia, had been to this stall in 2014 and snapped photographs — included in this study — of a live raccoon dog in a metal cage, stacked above crates of poultry, with the whole assembly sitting atop sewer drains. Notably, in the study from the China CDC, sewage at the market tested positive for SARS-CoV-2. Amy Maxmen