Friday, April 17, 2020

Cambridge University scholar : Earliest spread of SARS-CoV-2 started in China, probably from Guangdong

Report by : Gan Yung Chyan
                 / KUCINTA SETIA

Image : Workers in protective clothing were cleaning up the Wuhan Huanan Seafood Market in Wuhan. It was once thought to be the birthplace of the virus SARS-CoV-2 of the disease COVID-19. Courtesy of China News Network.




Peter Forster, the first research writer of the paper "Phylogenetic network analysis of SARS-CoV-2 genomes"(published by the Proceedings of the National Academy of Sciences) and a geneticist at the University of Cambridge, said in an interview with Voice of America (VOA) that although the exact origin of the virus cannot be determined yet, it is certain the earliest spread of COVID-19 (covid, in short) is in China, and the earliest epidemic location may not be in Wuhan, but in Guangdong, which is further south than Wuhan.

Foster and his colleagues used 160 complete viral genome data sampled from around the world from 24 December 2019 to 4 March 2020 to draw a map of the original spread of covid and found that the virus SARS-CoV-2 (covi, in short) has mutated into three different variants A, B and C.

Their study found that the novel coronavirus type A is closest to the coronavirus found in bats, the original virus. Although type A virus appears in Wuhan, it is not the main virus type in Wuhan, but the type B virus produced by the type A virus mutation is the main virus circulating in Wuhan. The B virus spread not only in Wuhan, but also in other parts of China and throughout East Asia. The main epidemic areas of type A viruses are the United States and Australia. The type C virus prevalent in Europe was mutated from the type B virus and was found in early cases in France, Italy, Sweden and the United Kingdom. This type of virus was not found in the study's mainland China samples, but it was found in Singapore, Hong Kong, and South Korea.

But can this prove that the covid virus originated in the United States?

Foster told VOA, "What we saw was the" founder effect ". So in early January, we didn't see the type A (virus) in the United States, but then we saw it. Look The situation is that some people who have traveled to Canada and North America have carried the type A (virus). Through the 'founder effect', it has not been discovered for a long time but it has spread and is highly contagious. Then, suddenly, the type A virus became the main type in the United States. So, this is what we call the 'founder effect'. This does not mean that because it is the majority of the United States, it is from the United States. This is a wrong conclusion. "

Foster said that their research could not accurately infer the source of the virus, but what is certain is that covi first spread in China.

He said, "I'm pretty sure that the (virus) was originally spread in China, or maybe in southern China. But this does not rule out such a possibility, for example, a crazy scientist, let's say a Madagascar scientist, A virus was artificially created in his / her garage laboratory, and then went to China, where the virus was dropped. This is indistinguishable from the data. But what I can say is that the virus spreads very early It happened in China. "

Foster also said that in view of the media's strong interest in the source of covi, he specifically studied a limited number of virus samples early in the outbreak. These virus samples show that the place where the virus first began to spread was not Wuhan, but more southward, possibly Guangdong Province. But he also emphasized that considering the limited sample size, this is only a preliminary inference.

He said, "As of that time (17 January 2020), I think we have a total of 44 samples from Wuhan. As of 17 January 2020, 42 of them are type B and only two are type A, so Wuhan doesn’t look like it was an early transmission site of type A (virus), 42-2, right? But if we look at the samples from other parts of China at that time, there are only 11, so very few. But among these 11 samples, there are 7 are type A and 4 are type B. Type C did not exist at that time. So, if I look at where these samples happened, they happened in Shenzhen and in Guangdong. So, the source of the virus should be in southern China. ”That is, the earliest virus samples came from China on 24 December. Our team also calculated that covi spread earliest between 13 September and 7 December 2019 within China. "

As for why the type A virus closest to the source of the new coronavirus is more common in the United States and Australia, the Foster team ’s research believes that the localization of type B virus in East Asia may also be caused by the "founder effect", that is, the "gene bottleneck" , That is, when the virus establishes a new type from a small, isolated infected group.

Another explanation is that the type B virus in Wuhan may be more immune and environmentally adaptable to a large part of the East Asian population. For regions outside East Asia, the virus needs to mutate to overcome its resistance. This is reflected in that at the initial stage, the mutation rate of covi in East Asia is slower than in other regions.

Foster also stated that when the covid outbreak first broke out in the West Coast of the United States, the virus should have been introduced from East Asia, but then during the New York outbreak, the virus came from Europe.

"I think the early cases were on the Pacific coast. In my opinion, they seem to have been imported from East Asia. Now, recent studies have shown that the cases in New York are from Europe, and several samples I have seen seem to confirm at this point.", he said.

Ref : https://www.voachinese.com/a/genetic-research-shows-covid19-first-spread-in-china-20200415/5372620.html

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