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Strains of COVID-19 virus

Date: 06 March 2020 Tags: Miscellaneous


A preliminary study conducted by researchers from Peking University’s School of Life Sciences and the Institut Pasteur of Shanghai has found two strains of the SARS-CoV-2 virus, behind the current coronavirus infection crisis.



  • As per the study, one of these strains is more aggressive than the other, and was associated with 70 per cent of the analysed strains. The researchers have also said that the prevalence of the more aggressive strain decreased after January 2020.

  • The researchers downloaded 103 publicly available SARS-CoV-2 genomes. After analysis, they identified mutations in 149 sites across the 103 sequenced strains.

  • Within the 103 genomes, one of the two strains of the SARS-CoV-2 was more prevalent. The researchers have called the two strains ‘L’ and ‘S’ types.

  • The researchers maintain that while the L type was prevalent in over 70 per cent of the cases analysed, the S type of the virus is the ancestral version, which means that the L type is derived from the S type and it transmits and replicates faster in human populations. Because of this higher transmission rate, the L type is considered to be more aggressive.

  • The researchers propose that due to heightened human interventions beginning in January 2020, the L type might have faced “selective pressure”, which the S type did not because of different epidemiological features of the two strains. Due to this its frequency decrease in other places after the initial breakout in Wuhan.

  • They, however, caution that their hypothesis is based on genomes that were collected from different locations at different points in time, due to which the results may not be comprehensive.

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