Covid-19
Since I am neither a virologist nor an epidemiologist, people constantly ask me to explain various things about the Covid-19 pandemic. Recently the most puzzling thing for many has been the emergence of "new variants". So let me explain.
1. Remember, everything in biology makes sense only from the evolutionary point of view.
2. Covid-19 is an RNA virus, so it mutates all the time, just like flu virus (although not at exactly the same rate). Viruses carrying various mutations compete with each other.
3. Until recently, the virus was spreading in a previously unexposed population. So the only mutations that gave it advantage were those that allowed it to spread faster. (Lower or higher mortality of the hosts is of little consequence for the virus, so there is little or no selection for that.) The viruses that were better at infecting more people outcompeted others.
4. Now a lot of people in many countries have acquired immunity. So the most beneficial mutations for the virus are now those that allow it to get around that immunity. Viruses carrying such mutations are spreading faster and outcompeting the old versions.
5. Soon, some countries will have significant chunks of their populations vaccinated. So the most beneficial mutations for the virus will be those that will allow it to get around vaccine-generated immunity. Such versions might already exist, but they don't have much competitive advantage yet. In a few weeks or months, they will be rapidly replacing all other versions of the virus.
6. How will it end? Considering that some countries haven't even started vaccinations, there will be plenty of time for the virus to evolve into versions that are not stopped by current vaccines. There is high probability that we'll need annual or semi-annual shots, just like with the flu virus.
7. Alternatively, there might be a limit to the virus's flexibility, and we might be able to eradicate it eventually. In any case, try to get vaccinated as soon as you can - just to improve your chances of winning this evolutionary race.
1. Remember, everything in biology makes sense only from the evolutionary point of view.
2. Covid-19 is an RNA virus, so it mutates all the time, just like flu virus (although not at exactly the same rate). Viruses carrying various mutations compete with each other.
3. Until recently, the virus was spreading in a previously unexposed population. So the only mutations that gave it advantage were those that allowed it to spread faster. (Lower or higher mortality of the hosts is of little consequence for the virus, so there is little or no selection for that.) The viruses that were better at infecting more people outcompeted others.
4. Now a lot of people in many countries have acquired immunity. So the most beneficial mutations for the virus are now those that allow it to get around that immunity. Viruses carrying such mutations are spreading faster and outcompeting the old versions.
5. Soon, some countries will have significant chunks of their populations vaccinated. So the most beneficial mutations for the virus will be those that will allow it to get around vaccine-generated immunity. Such versions might already exist, but they don't have much competitive advantage yet. In a few weeks or months, they will be rapidly replacing all other versions of the virus.
6. How will it end? Considering that some countries haven't even started vaccinations, there will be plenty of time for the virus to evolve into versions that are not stopped by current vaccines. There is high probability that we'll need annual or semi-annual shots, just like with the flu virus.
7. Alternatively, there might be a limit to the virus's flexibility, and we might be able to eradicate it eventually. In any case, try to get vaccinated as soon as you can - just to improve your chances of winning this evolutionary race.