Coronavirus: Two strains of virus identified with 70% infected by more aggressive variant, say experts
According to them, the older, milder strain seems to be becoming more common now
Scientists from China say they have identified two separate strains of the new coronavirus, and one is a more aggressive one.
The research team analyzed 103 publicly available genomes from infected persons and found 70% were the more aggressive type, while the remaining 30% comprised the less aggressive type.
The virus likely went through “mutations and natural selection besides recombination” that caused it to develop different strains, explain the researchers from Peking University, Beijing; the Chinese Academy of Sciences, China and Shanghai University, China, among others.
“We downloaded 103 publicly available SARS-CoV-2 genomes, aligned the sequences, and identified the genetic variants. We found that SARS-CoV-2 viruses evolved into two major types (L and S types),” says the team.
“These findings strongly support an urgent need for further immediate, comprehensive studies that combine genomic data, epidemiological data, and chart records of the clinical symptoms of patients with COVID-19,” recommends the team in their findings published in the National Science Review.
The set of 103 complete genome sequences was downloaded from Global Initiative on Sharing All Influenza Data (GISAID).
Coronaviruses (CoV) are a large family of viruses that cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). COVID-19 is a novel coronavirus — implying it is a new strain that has not been previously identified in humans.
In the current study, researchers say that the more aggressive type of virus — referred to as the L type — was found to be prevalent in the early stages of the outbreak in Wuhan — the epicenter of the outbreak in China’s Hubei province. The researchers think it may have evolved from the less aggressive type, which is being referred to as the S type.
However, the frequency of this type of virus has since decreased from early January, says the team. The older, milder strain seems to be becoming more common now.
“Although the L type (~70%) was more prevalent than the S type (~30%) in the SARS-CoV-2 viruses we examined, our evolutionary analyses suggested the S type was most likely the more ancient version of SARS-CoV-2. Our results also support the idea that the L type is more aggressive than the S type. Whereas the L type was more prevalent in the early stages of the outbreak in Wuhan, the frequency of the L type decreased after early January 2020,” says the study.
So, if the L type is more aggressive than the S type, why did the relative frequency of the L type decrease compared to the S type in other places after the initial breakout in Wuhan? A possible explanation is human intervention, says the team.
“One possible explanation is that, since January 2020, the Chinese central and local governments have taken rapid and comprehensive prevention and control measures. These human intervention efforts might have caused severe selective pressure against the L type, which might be more aggressive and spread more quickly,” explain the researchers.
They add, “The S type, on the other hand, which is evolutionarily older and less aggressive, might have experienced weaker selective pressure by human intervention, leading to an increase in its relative abundance among the COVID-19 viruses.”
The scientists, however, caution that their findings are based on a small sample size and more research is needed to have a better understanding of the evolution and epidemiology of COVID-19.
The World Health Organization (WHO) recently said that the world has entered into "uncharted territory" as it prepares to fight the coronavirus, which is circulating in more than 70 countries. “We have never before seen a respiratory pathogen that is capable of community transmission, but which can also be contained with the right measures. There is no choice but to act now," WHO Director-General Tedros Adhanom Ghebreyesus, had said during a press briefing.
According to the latest estimates, COVID-19 has killed 3,286 globally, and 95,425 people have been sickened by it.