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Asked by jazz449hug on 17 Jan 2022.
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Pam Vallely answered on 17 Jan 2022:
As you probably know genetic code is copied by enzymes and then translated into proteins which organisms (including humans) use to carry out their functions. Viruses are similar. A virus is just a piece of genetic code wrapped in a protein coat and some but not all have a fatty outer layer called the envelope surrounding them, the envelope often contains spike-like proteins sticking out of it, and these are what the virus uses to get in and out of our cells.
In humans and other organisms including bacteria the genetic code is always DNA. Viruses are different because although some of them use DNA as their genetic code, some use RNA. The enzymes that copy RNA are more error-prone than those that copy DNA, so often when an RNA viruses genome is copied mistakes are made. Usually the mistake means that the virus isn’t any good and so it doesn’t get copied again. But, occasionally the mistake gives the virus an advantage, it allows it to transmit more easily or get into a new cell type. In this case the mutated virus will be selected for and outgrow the viruses that don’t have the mutation. This is what is happening with SARS-CoV-2 at the moment. Because so many people around the world are infected and so much virus copying (or replication) is happening there are lots of opportunities for mutations to occur and the chances of a mutation that is useful to the virus happening is very high. So we saw the alpha variant becoming the common type in January 2020, then the Delta variant took over a few months later, and now the Omicron variant is dominant. Each new variant has an advantage over the last and allows it to transmit more easily. But the good news is that usually there is no advantage to a virus to destroy its host, so hopefully the virus will get better at transmitting, but less deadly over time.
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Valerie Vancollie answered on 17 Jan 2022:
Another way that viruses are able to mutate and change well is when they encounter someone with a weakened or compromised immune system. When this happens, the virus can infect that person for a lot longer than normal, sometimes months instead of 1-2 weeks. This increased exposure to an immune system means that it can evolve to better resist how we would normally resist or defeat covid.
There was a coma patient in the UK who got covid and scientists were able to monitor how it evolved and changed as doctors tried to fight it off. But it mutated a lot during this time.
This is why the current theory on Omicron is that it incubated in someone with a weakened immune system as it suddenly appeared with about 50 mutations. Since we didn’t see many in-between versions, it likely built up those mutations in someone with a compromised immune system, though we can’t fully prove that at present. Another possibility is that it went into another species and then jumped back to humans, but this is less likely.
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