Monday, March 30, 2020

What is the Relevance of the Different Strains of COVID-19?

In early March, a group of Chinese scientists analysed the genome sequence of the new coronavirus extracted from 103 patients. They found that the virus was not mutating into a more dangerous version, instead, they hypothesized that newer mutations are making the virus less deadly. Interestingly, they also identified two strains, one which they initially classified as very aggressive and the other as a less aggressive version. Nevertheless, with more information about patients’ outcomes and other available viral genomes, they changed this classification, to clearly identify which strain of infection will produce more severe symptoms.
Their disclaimer: “We now recognize that within the context of our study the term “aggressive” is misleading and should be replaced by a more precise term “a higher frequency”. These two virus types or lineages were named L and S. The L type is the more prevalent and S type is the “original” version found in Wuhan, China. The prevalence of the L type might be due to the selective pressure human interaction placed on the original S type.

It is clear now that COVID-19 impacts people differently, with some asymptomatic and others needing hospitalization (around 20-15%). Moreover, the strains are quite similar to each other as COVID-19 appears to mutate slowly, and key opinion leaders suggest that it appears unlikely the outcome differences are related to people being infected with different strains/types of the virus.
With more viral genome sequences to analyse from all over the world, now scientists have identified 8 strains. You can watch COVID-19 evolutionary development here:,2020-03-25,0,0,30000

Positive news coming from this global collaboration of research is confirmation that the mutation rate (the speed at which the virus changes) is 8 to 10 times slower than the one for the influenza virus. Therefore, when vaccines are ready ( hopefully in 12-18 months) they will be effective for a longer period of time, because they will be targeting the same type of slow-to-mutate viral particles.

One of the silver linings of this COVID-19 crisis is the revalidation and appreciation of scientific research and the subsequent boost in both funding and support for the scientific community and pharmaceutical companies.

COVID-19 Transmissions

Thanks Tom Keeter and Ilse Daehn for the edits


  1. Fascinating. 10 times more virulent and mutates 10 times slower. It is as if it "thinks" it is so advanced that it doesn't need to change anymore :) would have been a lot more successful it wasn't for the rare collateral damage of killing its host. Great post, thanks. I'd be interested to know how much it would need to mutate to fool the immune system and reinfect someone. Also any evidence of existing divergent strains being different enough to infect the person who already have the antibodies for one of them?