Chinese Scientists May Have Found Two Strains of Coronavirus

A joint study by scientists from numerous Chinese Universities led by Xiaolu Tang has found that the novel coronavirus can exist in two genetically different forms, called two different strains. Their findings have been published in the journal National Science Review on March 3. 

In samples collected from 103 patients, scientists have found that the SARS-CoV-2 exists in S and L strains. The S strain is milder and less prevalent (30% of cases) while the L strain is more virulent and is more prevalent (70%). The latter strain spreads quicker than the S strain, the older one, which means the L type evolved in due course. 

Interestingly, the L strain was found to be more prevalent in early stages of the outbreak in Wuhan, China, but its frequency decreased after January this year. This probably indicates that human intervention has put severe selective pressure on the L strain. In the case of the S strain there is less selective pressure due to which its frequency increased relatively. 

Notably, the new infection rate in China has seen a gradual decrease and rate of recovery of the patients has also increased. The probable factor can be the change in prevalence of the viral strain as found in the study. The aggressive measures that China adopted in curbing the spread of the virus could have put huge selective pressure on the more virulent strain. 

Viruses always undergo rapid mutation, especially RNA viruses like the SARS-CoV-2. This virus colonizes in the respiratory tract of a person that gets infected. During this process, the virus replicates in the respiratory tract and each time it replicates, genetic mutations occur. 

“I think it’s a fact that there are two strains.  It’s normal for viruses to undergo evolution when they are transmitted to a new host,” said Erik Volz of the Imperial College in London. 

But, whether the genetic variations found by Tang and his colleagues can be termed different strains is not beyond question. “In all practical terms, the virus is as it was when it originally emerged. There’s no evidence it is getting any worse,” said Ian Jones at the University of Reading, U.K. The difference between the two strains is said to be ‘tiny’ and Jones reportedly mentioned that they cannot be considered as two separate “strains”. 

Another factor is the small sample size of the study. As of now, more than 166 sequencing results have been collated. It may also be possible that more strains of the novel coronavirus actually exist. 

Nevertheless, the attempt to find out the genetic variations of the virus is essential for the development of a vaccine against it. The current study done in China, undoubtedly, has provided essential information about the evolution of the virus. Despite apprehensions, it is likely that the two strains as reported do exist in reality. The study however provides ample evidence for the existence of the two strains.  The study says that the evolution of the coronavirus into two major strains “are well defined by the two SNP (genetic variation at single point)s that show nearly complete linkage across the viral strains sequenced till date.”