Weekly Update On The Science Of COVID-19: Viral Evolution

Jun 3, 2020

The coronavirus that causes COVID-19 is starting to evolve. Scientists say that’s nothing to be alarmed about, but it does have implications for public health. In KNAU’s weekly update on the science of COVID-19, Melissa Sevigny spoke with Dr. Jason Ladner, a geneticist at Northern Arizona University, about why viruses change over time and what that could mean for developing a vaccine.  

Credit CDC

So we’re talking about viral mutations, which sounds a little bit scary. When we say a virus is mutating what exactly does that mean?

Really we’re just referring to the natural process by which replication errors result in the generation of viruses that are genetically slightly different from the progenitors, or the parent, viruses…. All biological organisms mutate every time the genome is replicated. It’s a natural process of biological life. Viruses do mutate more quickly than other organisms, it allows them for amazing evolutionary potential, but I want to take away that fear that comes when people see some headline talking about how a virus is mutating. I want people to understand, we don’t need to be scared about that. We understand that, that’s a process that happens, doesn’t mean that we don’t need to pay attention to it, to track it, to watch what’s happening, to see how it may impact our ability to diagnose or to treat these different viruses …So when you see a headline that says, Ebola virus is mutating, coronavirus is mutating, this is really not news. It would be news if it wasn’t mutating.

Let’s talk about this particular coronavirus, how has it been evolving over the last couple of months?

It’s been evolving at about the rate we’d expect. The estimates out there suggest it’s picking up about 2 mutations or substitutions every month.  It’s the average speed for a coronavirus, a little bit slow for other RNA viruses. Other RNA viruses like Ebola or influenza are maybe evolving at a slightly faster rate.

Let’s talk about what this means for public health. Do these mutations actually change the way the virus is behaving over time? Is it getting more dangerous, less dangerous?

I mean, that’s a great question that we don’t really know the answer to. I can tell you theoretically, the majority of the mutations that are occurring are going to be detrimental to the virus. Most of the mutations will create a virus that’s less fit…. The majority of the remaining mutations are likely to be neutral, have no benefit for the virus but have no determinate to virus. Some small fraction of those mutations can potentially have a benefit for the virus, can lead the replicate more efficiently, be able to transmit more efficiently… So it can happen. Is it happening, how much is happening, is it making an impact on the actual outbreak? Those are the million dollar questions right now…. because the only way we only know if a given mutation had some kind of replication or transmission benefit for the virus, is to conduct very careful experiments in a laboratory.

What does this mean for developing a vaccine for the coronavirus disease. Is it harder to develop a vaccine when the disease is evolving this way?  

Obviously the goal in developing a vaccine is to give maybe a single dose of the vaccine and for it to provide lifelong or at least very long term immunity. You can think of measles vaccination or chickenpox, something like that. If the virus is evolving very quickly, particularly if the virus is able to evolve quickly in the proteins that are recognized by the immune system… then it can be problematic. You see this with influenza, influenza is changing every year, that’s why we have a new flu vaccine and people are getting vaccinated every year. It doesn’t mean our flu vaccine isn’t effective, but the virus is changing so we need to be constantly vaccinated against new strains.

Jason Ladner, thank you so much for speaking with me today.

Thank you.