Scientists limit the source of the outbreak of the Covid-19 pandemic between September 12 and 2019, possibly starting farther south in China than in Wuhan.
The first human-borne outbreak of the new strain of coronavirus (SARS-CoV-2) may have occurred in southern China rather than Wuhan City, in Hubei province in central China. an international research group led by the University of Cambridge (UK).
Scientists have investigated the origin of the virus, analyzed samples of viruses around the world, and calculated the timeline for the Covid-19 pandemic to begin. They identified the first outbreak could have occurred between September 13 and December 7, 2019.
Look for milestone 0
“The virus may have mutated and reached the final variant to effectively infect humans a few months earlier. However, it stays in the body of a bat, an animal or even a person. Some months before you start jumping to other individuals, “said Peter Foster, Cambridge University geneticist, April 16.
“Then the virus began to spread and spread from person to person between September 13 and December 7, creating a network we present in the journal Proceedings of the National Academy of Sciences (PNAS).” He said.
The team analyzed the virus samples using a phylogenetic network (genealogy tree). They used genetic algorithms and gene mutation research to map the occurrence of viral strains globally, according to the South China Morning Post.
Also based on the method of studying the path of the virus based on mutations, scientists are seeking to estimate the location of the “zero patient” of the global pandemic. The group hopes to receive support from Chinese colleagues.
The first historical traces led the group to the south of Wuhan.
“If I had to answer now, I would say the original infection is more likely to start in southern China than in Wuhan. But to prove this, we need to analyze more samples of bats. another species has the potential to be a host, and samples were kept in Chinese hospitals between September and December, “Foster said.
Viruses in China are “younger” than viruses in the US
The Cambridge team attracted international attention with a scientific paper on the evolutionary history of the SARS-CoV-2 virus strain published in PNAS in April.
The scientists found that most strain strains in Australia and the US are genetically more closely related to the corona virus found on bats. Strains that are infected in East Asia are more closely related to the corona virus on bats. Meanwhile, most of the variation in Europe is a “descendant” of the strain that spread throughout East Asia.
Foster thinks that the first strain of SARS-CoV-2 may have started in China but is better able to adapt to the characteristics of the US population and environment. Therefore, the US strain of the virus is “older” and closer to the original version of the bat than the strain that is spreading strongly in East Asia.
However, the article says the team has only analyzed 160 strains of SARS-CoV-2 collected since the end of December 2019. The limited number of samples makes it difficult for scientists to pinpoint exactly when and where the first outbreak occurred.
In the latest research, pending review, Foster and colleagues from various research institutes, including the Institute of Forensic Genetics in Germany, expanded the database. They added 1,001 high-quality, sequenced samples of SARS-CoV-2, published by scientists around the world recently.
The more samples studied, the more accurately the team determined when and where the pandemic started. Through the “counting” mutation method, the scientists get closer to the goal of determining when “patient number 0” is infected with the germ closest to the corona virus in the bat.
However, according to Su Bing, a geneticist at the Kunming Zoological Institute in Yunnan Province, the method of phylogenetic network has some limitations when applied to redraw the path of spread of an epidemic. sick.
He argued that the Covid-19 pandemic was an unprecedented infection outbreak, so the SARS-CoV-2 virus may have undergone many changes with the model being beyond prediction.
“It cannot be completely accurate. There will always be tolerances. This research may open up important clues for future investigations, but need to look at those conclusions carefully,” he said. price.