A graphic depicting the evolution of the novel coronavirus and the locations where variants were identified, from the paper "Phylogenetic network analysis of SARS-CoV-2 genomes" appearing in the Proceedings of the National Academy of Sciences of the United States of America.

TOKYO -- The novel coronavirus now sweeping across the globe in fact has three broad variants, according to genome evolution analysis by a University of Cambridge-led research team published April 8 in a U.S. scientific journal.

The team analyzed sample genomes of SARS-CoV-2 -- the virus' scientific designation -- taken from 160 COVID-19 patients in different parts of the world between late December 2019 and early March this year. Based on the results, the researchers believe the virus mutated into the three broad types -- A, B and C -- as it progressed, from when it made a likely jump from bats to humans, to its epidemic spread in Wuhan, central China, to its eventual devastating arrival in Europe, North America and beyond.

The paper, published in the Proceedings of the National Academy of Sciences of the United States of America, goes on to note that mutations may affect how COVID-19 presents, and how the virus spreads. The team's classification could be used to track variants of the virus and help confirm these effects in the field, "and when designing treatment and, eventually, vaccines," the paper continues.

According to the study, versions of variant A -- which is closely related to bat coronavirus -- were found in samples from patients in Wuhan and Guangdong province, southern China, as well as in Japanese and American patients. There were also instances in Australia. In fact, 15 of the 33 people in the A group were found outside East Asia.

For variant B, 74 of the 93 viral genomes were sampled in Wuhan, parts of eastern China, and scattered in other East Asian countries. The remainder were discovered in the U.S., Canada, Mexico, France, Germany, Italy and Australia. Variant C, meanwhile, is the main version seen in Europe, including France, Britain, Italy and Sweden, though there are also cases in Brazil and California. However, no examples of variant C were found in mainland China, though there were cases in Hong Kong and, further afield in Asia, South Korea, Singapore and Taiwan.

Meanwhile, the U.S. website Nextstrain, which tracks the evolution of infectious diseases, publishes continuous updates on the mutation of the novel coronavirus, based on samples drawn from COVID-19 patients in different countries around the world. The virus' evolutionary tree suggests that it began mutating with the first outbreak in China, before variants made the jump to the U.S., Europe, Japan and other places.

According to University of Tokyo associate professor and geneticist Jun Ohashi, "If progress can keep being made on analysis of the virus' genome, we can make observations about whether certain variants cause more severe illness, and that should enable us to narrow down candidate molecules for use in a vaccine or treatments."

(Japanese original by Ayumu Iwasaki, Science & Environment News Department)