Now in the world there are three types of SARS-CoV-2 virus. The unevenness of their distribution gives scientists the opportunity to predict future outbreaks of the disease.
Researchers from the University of Cambridge studied the phylogenetic evolution of SARS-CoV-2 coronavirus and found out what mutations it underwent, migrating from Asia to other parts of the world. An article about this is published in the publication Proceedings of the National Academy of Sciences.
In their work, scientists analyzed 160 complete virus genomes obtained from patients with severe COVID-19 symptoms. During the study, three major genetic variants of SARS-CoV-2 were identified. The authors of the work assigned them the index A, B, and C, respectively, according to the time of origin.
However, the spread of virus variants was very unexpected. So, the initial type A, which was transmitted to people from bats and with which the epidemic in Wuhan is most likely to start, turned out to be far from the most common in China and in East Asia as a whole.
It turned out that types A and C are more common in Europe and the USA. In East Asia, type B became the most frequent: at the same time, it spread outside the region, mutating into derived types. This can be either a consequence of the founder’s effect or a sign that a marked immunological and environmental resistance to type B SARS-CoV-2 is observed outside Asia.
But the picture of the spread of various types of virus is far from uniform everywhere. So, despite the predominance of varieties A and C in Europe, the most common type in Switzerland, Germany, Belgium, and the Netherlands turned out to be type B. This fact indicates that the virus could get to these countries directly from China.
But the first cases in Italy, France, England, and Sweden revealed exactly type C. In mainland China, this type of coronavirus is completely absent, however, isolated cases of type C infection have been found in other countries and regions of Southeast Asia: Singapore, South Korea, and Hong Kong.
A detailed study of genomes allowed scientists to trace the pathways of mutations and the spread of pathogens. In some cases, the pathways of the virus were such that experienced travelers could be envious. For example, the viral genome obtained from a Mexican patient (COVID-19 was diagnosed on February 28) “migrated” from Italy. Moreover, the “Italian” subtype of the virus came from the first documented patient in Munich; he, in turn, was infected by a colleague from Shanghai who had received the virus during a trip to Wuhan with his parents.
The work carried out by scientists from Cambridge allows not only to shed light on the evolution of the virus but also to predict the next outbreaks of the disease and take preventive measures. Scientists also noted that we should expect the emergence of new types of SARS-CoV-2 in the near future: in order to overcome the stability of the immune system, the pathogen needs to change.