A study by Chinese scientists has shown that there is more than one type of the novel coronavirus that is sweeping across the globe, infecting around 110,000 people. The first strain is less aggressive and the second more virulent.
The scientists, headed by Tang Xiaolu, compared the genetic sequences of samples of 103 patients positive for Covid-19 and their research showed that the more aggressive strain of the coronavirus, the “L” type, appeared as the more dominant one when the virus first appeared in Wuhan last December. But as the disease spread, it seems that this strain receded.
In samples that were collected at a later date from different parts of China and from other countries, another strain emerged, the more common “S” type.
According to the scientists, the genetic material of the “S” type was closer in nature to the coronaviruses found in pangolins and bats, which are the two animals suspected to have hosted the virus before it was transmitted to human beings. This “S” type, the scientists believe, is less aggressive.
Additionally, the Chinese scientists, whose report was published in the National Science Review on March 5, say that the “S” type may have actually made the jump to humans earlier than believed, but was mild enough as to not alarm doctors.
From the 103 genetic sequences the scientists studied, 30 per cent fell under the “S” type, and 70 per cent were classified as the “L” type. The scientists, therefore, concluded that the “S” type spreads and replicates slower than the “L” type, and also has fewer derived mutations.
The scientists wrote: “Thus, our results suggest the L might be more aggressive.”
However, to complicate matters, there are Covid-19 patients whose genetic make-up shows traits that are not from the “L” and “S” types, the scientists said.
Another thing that they noted was that in Wuhan, 26 out of 27 viruses isolated from patients were from the “L” type, while outside of the city, the figure falls at around only 60 per cent of the virus classified as the “L” type.
This led them to conclude that the “L” type was much more prevalent in Wuhan than in other places, but due to the stringent lockdown measures in the city enforced by the Chinese authorities, this type was prevented from being spread outside Wuhan.
The scientists wrote: “These human intervention efforts might have caused severe selective pressure against the L type.”
However, they cautioned that some patients could have both strains at the same time, as is the case with one patient in the United States whose sample virus sequence showed both “L” and “S” types of the coronavirus.
According to the scientists, “although novel mutations could lead to this result … we inferred this patient might have been infected by at least two different strains of Sars-CoV-2”, referring to the coronavirus that causes Covid-19.
Meanwhile, the authorities from the World Health Organization have said that the findings of the Chinese scientists are preliminary and that the public should know “it’s important we don’t overinterpret” them.
Dr Mike Ryan, the official coordinating the agency’s response to the Covid-19 epidemic, said of the two strains reported: “It’s got a slightly different signature, but it’s not a fundamentally different virus.”
And scientists from the MRC-University of Glasgow Centre for Virus Research in Scotland have said that they believe the authors of the Chinese study should retract the paper, as they claim the scientists misinterpreted the data in the study as well as did not take into account limitations in their statistical methods.
“Given these flaws, we believe that Tang et al should retract their paper, as the claims made in it are clearly unfounded and risk spreading dangerous misinformation at a crucial time in the outbreak.” /TISG