Researchers at the institution’s tropical botanical garden examined the genomes of 93 samples of Covid-19, collected from 12 countries on four different continents, as well as the sources of contamination and the routes of transmission.
Detected at the Huanan seafood market, the new coronavirus originated from another location and quickly spread to the market and beyond, the scientists said.
Three ways of contamination
At least three routes of virus transmission were discovered during the examination of 59 haplotypes (genome fraction) from 93 samples. According to the study, these groups of alleles can be divided into five groups, three of which represent old contaminating agents, for example, H1, H3 and H13, while two others are new (H56 and mv2).
For example, samples from patients contaminated by the seafood market show the H1 haplotype and its derivatives, while samples from some patients in Wuhan contain the H3 haplotype, which is unrelated to those found at the cited market.
By taking into account the time of the onset of contamination and the spread of the disease, the researchers concluded that the Huanan market was not the source of the coronavirus. This is confirmed by the presence of the older H13 and H38 haplotypes found in patient samples from Shenzhen (the first case of infection in Guangdong province) and Washington (the first case in the United States).
These individuals should have been infected during their trips to Wuhan between late December 2019 and early January 2020. However, the H13 and H38 haplotypes were not discovered in Wuhan patients.
Thus, the transmission of the virus would have started in late November or early December 2019, and would have accelerated when Covid-19 was introduced to the seafood market, the researchers concluded.