A new study by European researchers found three different types of CCP virus genomes spreading around the world.
The Cambridge study, titled “Phylogenetic network analysis of SARS-CoV-2 genomes”(pdf), was published last week by Proceedings of the National Academy of Sciences (PNAS).
It studied the first 160 complete viral genomes from the earliest patients across the world, between Dec. 24, 2019 and March 4, 2020. It then mapped the family tree of the genomes.
The 3 Types
The genomes are categorized into three distinct types: A, B, and C, within each cluster the genomes are closely related.
Type A is considered the root of the outbreak, since it has the highest similarity to the bat virus.
Among the 44 samples of type A, 16 are from mainland China. Of the 16, two from Wuhan and four from Guangdong carry the ancestral genome. One is from Hong Kong and one is from Taiwan.
Nine are from other Asian countries and carry mutated version of A.
Another nine are from America, also carrying mutated versions of A. Two of the American patients are reported to have lived in Wuhan.
Five are from Australia and three are from Europe.
Type B is mutated from A. Among the 93 cases, 58 are from Mainland China, Hong Kong, and Taiwan, 16 are from other Asian countries, eight are from the United States, three are from Canada and Mexico, seven are from Europe and one is from Australia.
Type C, the daughter of B, was most common in Europe, with 11 out of 23 C cases seen in early patients from France, Italy, Sweden, and England. Of the rest, six are from Asia, two are from Australia, and one each are from Taiwan, Hong Kong, the United States, and Brazil.
Dr. Sean Lin, former lab director of viral diseases branch at Walter Reed Army Institute of Research, said this further confirmed scientists’ hypothesis that this virus is constantly mutating.
“First, the SARS-CoV-2 virus did mutate aggressively in the human body in different regions. Secondly, the virus may undergo further adaptation when they encounter different races, in different continents,” Lin told NTD News.
In this study, the key nucleotide difference that distinguish the three types are not located in the gene regions that encodes the spike protein, “this suggest even though the spike protein are very important in binding cellular receptors, but other viral factors are also critical in data-mining virus, pathogenicity and immunogenicity,” he added.
Tracking the Origin
Lin said this report also shows that, phylogenetic analysis are very useful in tracking how the virus is spreading globally. For example, type A is the root of B and C, even though many of the U.S. cases belong to type A. But several Chinese cases also belong to type A and six of them carry the ancestral genome sequence of Type A, which means many of the U.S. cases can be tracked back to the cases in Wuhan, China.
“This report clearly suggests that all these cases can be traced back to Wuhan, China, and the Chinese communist regime has been blaming the United States or Italian as source of the outbreak. [This proves] those claims are totally groundless.” said Lin.
Mount Sinai conducted another study published this week that suggests the virus in New York was brought there by people arriving from Europe.
It also shows a case of the virus in Washington state came from Wuhan, which agrees with the study mentioned earlier.