New evidence about the origin of Covid-19

New studies support the hypothesis that nCoV originated from animals and spread to humans in late 2019. The epicenter of the outbreak continues to be the Huanan market, Wuhan, China.

According to CNN, these three studies were published on scientific data pages on February 26 before being published in specialized journals. The authors highlight evidence that nCoV originated from animals and jumped to humans because of wildlife trade in the Huanan seafood market, Wuhan, China. They also rejected the idea that nCoV was cultured in a laboratory.

Strengthening evidence that nCoV originated from wild animals

Two studies, conducted by a team of experts from the University of Arizona, USA, used spatial analysis to show that the earliest Covid-19 cases appeared in December 2019. Environmental samples with close links to wildlife sellers at Huanan Seafood Market, Wuhan, China.

Through these two studies, the expert team also opposes the theory of the laboratory origin of nCoV, asserting that there is no evidence that the virus leaked from here.

Professor Michael Worobey, Dean of the Department of Evolutionary Ecology, University of Arizona, and the author of the two works, said that these results provide the strongest and most groundbreaking evidence for the origin of the Covid-19 pandemic related to the COVID-19 pandemic. animals or originating from the animals themselves. He called the findings 'couldn't be more plausible' about the origin of nCoV.

"When you look at all the evidence together, it's a clear picture to conclude that the pandemic started with the Huanan seafood market," the expert asserted.

Members of the Wuhan Sanitary Emergency Response Team leave the Huanan Seafood Market after it closed on January 11, 2020.

Meanwhile, epidemiologist Dr Thea Fischer, University of Copenhagen, Denmark, who was not involved in the studies, called the findings 'very convincing'. According to the NY Times, he thinks that the question of whether the virus can be transmitted from animals to humans has been resolved with good evidence.

Prof Worobey described the initial transmission pattern of nCoV as similar to a fireworks display. The initial outbreak occurred in late 2019. But, by early January-February 2020, the pattern had completely changed, showing that a virus had 'infiltrated local communities'.

The study wrote: "In December 2019, Covid-19 cases suddenly concentrated in the market at the Huanan seafood market, regardless of whether they were market sellers, had visited here or were related to the area. in this area or not. Some cases related to epidemiology with the market are located in the west, where most of the wildlife stalls are located'.

When examining surfaces at the market for nCoV genetic material, one stall had many positive clues, including a cage that a researcher had previously discovered was where badger dogs were kept in captivity.

Staff wearing protective gear disinfecting the Huanan market on March 4, 2020. (Photo: Reuters).

Theory of two different strains of nCoV spreading from animals to humans

In the other study, a team of experts from the Chinese Center for Disease Control and Prevention (CDC) discovered that the SARS-CoV-2 genome before February 2020 consisted of two evolutionary branches of the virus - denoted as A and B. These two clade are the result of at least two events of animal-to-human cross-transmission.

This study was conducted two years ago, but until now, the team of experts from China CDC has only published the results.

The first transmission from animals to humans, possibly related to the B-series virus, occurred in late November and early December 2019. Meanwhile, the emergence of the A line can occur several weeks after the first event.

These findings define the gap between the time when nCoV first entered the human body and the first cases of Covid-19 were reported. Similar to SARS-CoV-1 in 2002, 2003, the emergence of SARS-CoV-2 may also be due to many events of transmission from animals to humans.

The main special feature is that there are two corona strains that jump out of two different animals to humans. The time could be in November 2019.

Dr. Worobey and colleagues analyzed 800 samples of Covid-19 patients at the beginning of the pandemic. They found that both lines A and B experienced separate growth spurts. The team of experts believe that the most likely explanation is that both strains spread themselves from different animals to humans.

In particular, both of these transmissions can occur in the Huanan market. Dr. Worobey and his colleagues found that the two earliest cases of Covid-19 of the A lineage involved people living near the market. Meanwhile, a study by the China CDC revealed that the gloves collected in this market had the line A.

The researchers speculated that the dog badger could be an intermediary for the transmission of nCoV from animals to humans. In the photo is a dog badger that was sold at the Huanan seafood market, Wuhan, China.

These findings surprised scientists. In the early days of the pandemic in China, cases of Covid-19 were only discovered related to branch B virus. Because it seems to develop after branch A and some researchers think that nCoV only appeared. in the market after spreading somewhere around Wuhan.

However, this logic has been broken. This finding is consistent with the scenario proposed by Dr. Worobey and his colleagues, which suggests that at least two events cause nCoV to jump from animals to humans.

The authors note that the initial timing may include more viruses, but most of them cannot survive in humans, only nCoV can achieve that. In addition, when looking at reports of nCoV infection in animals such as cats, deer, and hamsters, the researchers found that 'this is a virus that doesn't need to care about who the host is for it to replicate'.

However, none of these studies had definitive evidence of any animal species that could be the vectors of the virus's transmission to humans. For now, they hypothesize it could be a dog badger or another mammal. This is also an issue that some experts say the research is still limited.

Professor of immunology Robert Garry, Tulane Medical School, USA, in an interview with CNN: 'These findings are almost certain that the virus that we have is of animal origin. Professor Garry is a co-author of the second study. He and his colleagues found at least two facts that reinforce the evidence that nCoV was transmitted from animals to humans.

Virologist Kristian Andersen, of Scripps Research Institute in La Jolla, California, USA, co-author, asserts that the most important thing is to find the wild mammal species that were sold in the South China market during that time. November 2019 and look for evidence of past outbreaks. He suggested that it is possible that villagers in places where wildlife are supplied have carried antibodies due to corona virus exposure.