Why Viruses Mutate, Explained by an Infectious Disease Expert

by -

COVID-19 virus with purple COVID-19 variant

You’ve probably heard a lot about COVID-19 variants. Infectious Disease Expert Dr. Rossana Rosa, UnityPoint Health, identifies three things you should know about virus changes, especially during the COVID-19 pandemic.

How Do Viruses Evolve So Quickly?

Viruses aren’t living things. They need a host to survive – like the cells in your body. Once a virus enters your body, it reproduces and spreads. The more a virus circulates in a population of people, the more it can change. All viruses change but not always at the same rate. 

“The rate of change varies from virus to virus. Some change very fast, such as the influenza virus. That is why we get a new flu vaccine every year. SARS-CoV-2, the virus that causes COVID-19, has taught us a lot. Current research suggests it changes at a slower rate than influenza. Time is still needed to determine if that means we’ll need more than just an initial dose of the vaccine for COVID-19,” Dr. Rosa says.

Because viruses are always changing, it's very important to stay up-to-date on all vaccines.

What's the Difference Between Mutations, Variants and Strains?

  • Mutation. When a virus replicates, and the end copy has differences (in DNA or RNA), those differences are mutations.
  • Variant. When you accumulate enough mutations, you get a variant.
  • Strain. When you can prove a variant truly has new biologic capabilities then you can call it a strain.

“With COVID-19, the changes to the virus are currently called variants. More research is needed to determine if any of the variants can be called a strain. Variants are often referred to by the physical location of where they were identified. It doesn’t mean that’s always where the variant developed. Right now, there are four main COVID-19 variants on the radar – the UK (B.1.1.7), Californian (CAL.20C), South African (B.1.351) and Brazilian (P.1) variants,” Dr. Rosa says.

Why is it Important to Focus on the Impact of the Virus’ Change?

“What matters is the impact the changes have on the virus itself. So, some viruses might have a few differences – a few mutations – but there are no noticeable changes to the virus. Sometimes viruses can have mutations that give the virus an advantage, whether that’s a better attachment to cells or the ability to replicate faster. Mutations can also result in disadvantages for the virus, lowering the ability to attach to cells or taking longer to reproduce,” Dr. Rosa says.

The important things for scientists to identify about changing viruses, like the virus that causes COVID-19, is how the change impacts people, if the vaccines still work and if tests can still identify the active virus.

“For COVID-19, researchers are interested in the UK, Brazil and California variants, because they seem to be associated with either higher transmissibility or potentially higher death rates. Scientist are keeping a close eye on the South African variant because the vaccines seem to be less effective against it. At this point, current PCR testing and rapid testing can detect all COVID-19 variants,” Dr. Rosa says.

What Causes Viruses to Mutate?

Virus changes are associated to three things. First, sometimes a change in a virus is a pure error.

“I heard this really good analogy about virus changes,” Dr. Rosa says. “It's like copying a manuscript and, at some point, you're going to have a typo.”

Another reason a virus might change is because of pressure from select cells in the body.

“This hypothesis emerged regarding some of the COVID-19 variants. It states if a virus infects a person who doesn’t have a very strong immune system, for example, someone with cancer, then the body is not able to clear the virus very well. Then the virus can say, ‘Hey, how are you going to attack me and make changes based on that?’,” Dr. Rosa says.

The creation of a vaccine for any new virus could also cause additional mutations.

“Any virus is going to try to keep changing so it can continue to spread. For COVID-19, that means we’ll likely see more new variants as more people are vaccinated. That’s natural and expected. Don’t be too worried about it, the vaccine should help keep us safe. But, that’s why it’s so important for experts to work together around the world to track the COVID-19 variants. It’s also important for you to continue doing your part by getting vaccinated as soon as you become eligible to get the COVID-19 vaccine,” Dr. Rosa says.

Finally, no matter what the mutation for COVID-19, you can still help prevent the spread of the disease by wearing a mask, social distancing and avoiding crowds. These efforts will also protect you from other viruses in circulation, too.