Two different strains of the Wuhan coronavirus are already circulating

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At least two different strains of the Wuhan coronavirus or SARS-CoV-2 are already circulating. This is indicated by a recent study that shows that there is a predominant type of pathogen, with greater transmission capacity and possible aggressiveness (associated with the outbreak in China); and another less frequent and, a priori, also less virulent (with greater presence outside the Asian country).

The work, led by Xiaolu Tang, from Peking University and the Sanghai Pasteur Institute, has analyzed the genetic information of 103 virus samples . According to their conclusions, approximately 70% of the analyzes corresponded to the one designated as type L, while the remaining 30% was of the type S call.

According to the researchers, their epidemiological analysis seems to indicate that type L has a greater capacity for cellular transmission and replication, and can be considered as of greater virulence, an appreciation with which Jordi Reina, chief of Virology at the Hospital Son Espases de Mallorca.

On the other hand, for Isabel Sola, director of the Coronavirus Laboratory of the National Biotechnology Center (belonging to the CSIC), the analysis does not provide sufficient data to determine the virulence of the variants. "This study proposes that, since there are more sequences L than S, the variant L seems more prevalent, which makes them suggest that it may be transmitted easier. But this does not have to mean that it is more virulent," he says. .

Type S, according to the work published in the National Science Review of the Chinese Academy of Sciences, "is the ancestral genetic form " of the pathogen from which, later, the predominant type L was derived.

But, despite this preponderance of type L, analyzes confirm that, outside the borders of China, type S, the least virulent according to its data, has been gaining weight.

While 96% of the samples analyzed from Wuhan (27 of the 103 total) corresponded to type L, in the genetic analyzes performed on the samples taken abroad (73 of the 103) there was greater divergence: 61.6 % were of type L and 38.4% corresponded to type S.

This greater presence of the S type outside of Wuhan could be due, according to the researchers, to "the control and prevention measures " of the infections that the Chinese Government implemented in January 2020.

Type S, "could have experienced weaker selective pressure ," added the scientists, who, however, point out that more research is needed to confirm their hypothesis.

"In general, less pathogenic viruses are better established in the population," said José Antonio Pérez Molina, an infectious specialist at the Ramón y Cajal Hospital in Madrid and member of the Spanish Society of Infectious Diseases and Clinical Microbiology ( SEIMC), who is not surprised that different strains of the virus already circulate, since it is a normal behavior in this type of microorganisms.

"This study shows us the constant genetic evolution of SARS-CoV," agrees Reina, who clarifies that it has not yet been established whether the evolution occurred in humans or in an animal host.

Both specialists agree that the monitoring of the genetic evolution of the pathogen is key because it will determine the real impact on the human population. "If we detect clinical changes in the disease, it is important to know what the virus is that is causing them," says Pérez Molina.

In general, they explain, it is usual to select those variants with greater diffusion capacity but also with lower lethality.

In their conclusions, Chinese scientists demand more studies that combine genomic data, epidemiological information and medical records with clinical symptoms of patients with Covid-19.

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