Wednesday, May 06, 2020

There may now be over 30 strains of COVID-19 ... or there may not

Viruses, particularly RNA-based viruses like coronaviruses, have a tendency to mutate. So, it's no surprise to find that COVID-19 now comes in a variety of different strains.
Back in early March, scientists in China were reporting that the virus had split into two separate strains, one more contagious than the other. Since then, I have seen claims of 3 strains, 8 strains, 14 strains.
Now, another Chinese study has identified over 30 different strains, which definitely does not bode well for the search for a vaccine. These different strains are found in different parts of the world, and some are more contagious than others, and some are more deadly than others. The most aggressive strains were found to be able to generate up to 270 times the viral load of the weakest. The deadliest mutations in the study were found in Europe, while the strains found across the USA were typically among the milder ones.
The study (still not peer-reviewed) points out that identifying the particular strain operating on a region could help determine the action required to fight it (currently all COVID cases are essentially treated alike). Any potential vaccines certainly need to take the different strains into account.
Other studies have pointed to at least two mutations of the spike proteins that the virus uses to latch onto and invade cells, which could have important implications for the way the virus spreads, and on the developnent of potential vaccines.
However, it is still not entirely clear that the virus has in fact mutated into significantly different forms, and some virologists believe that this kind of scientific scare-mongering is unjustified and counter-productive. Indeed, many scientists believe there is actually only ONE strain of the virus. Yes, like with all viruses, mutations have occurred as transcription errors accumulate over time. But for a new strain to be recognized the mutations need to be substantial, either in terms of the virus' tranmissibility, virulence, antigenicity or resistance. It has not been proven to the satisfaction of many that COVID-19 - which has been shown to have a much slower mutation rate than, say, the influenza virus - has actually branched into lineages that are materially different from the original.
So, although some of these reports about wildly mutating virus strains make for good sound-bites and dramatic newspaper articles, the reality, as Ed Yong explains in some detail in this Atlantic article, is that ... it's complicated.

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