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Science and Innovations

Weekly Update With Dr. Paul Keim: Understanding Coronavirus


Arizona scientists have joined forces to study the coronavirus disease in a new institute called the Arizona COVID-19 Genomics Union. The group’s co-founder is Dr. Paul Keim, an infectious disease expert with Northern Arizona University and the nonprofit institute TGen North. He spoke with KNAU’s Melissa Sevigny in the first installment of a regular weekly update about the science of COVID-19.

So we know the coronavirus disease is a new disease to humans, so how did that happen?

Coronaviruses do exist in humans. This is the seventh recognized coronavirus…. This particular one follows the same pattern we saw with SARS and MERS, in that it existed in an animal reservoir, quite likely bats. We don’t know a lot about that, but the idea is it’s tolerated, maybe causes mild disease, in bats, and then it undergoes natural evolutionary processes. For example, one of the differences that we know exists between this virus and the bat viruses is in the region of the spike protein. Everybody’s seen these picture of the coronavirus, it’s a round little ball and it has these spikes coming out. Artists like to color those spikes red, they’re not really red, but that makes for an attractive looking virus on the TV screen. Those spike proteins are really important for the virus when it infects humans. The virus comes into our respiratory tract and binds to cells in our respiratory tract via the tips of those spikes…. So the mutations that occurred to allow that virus to jump from animals to humans, definitely one of the most important mutations that occurred is right at the tip of those spikes.

Do scientists know when that occurred, that jump from animals to humans?

When we look at the genome of this… we can look at different lineages of the virus and then calculate back to what we call “the most common recent ancestor.” We can then estimate the time when this thing jumped. The best estimates right now are late November to early December 2019. That timing gives us a perspective on how fast this thing has been transmitted around China and then the whole rest of the world. I mean, we really are a global community. All the cases in the entire world that we’re seeing now are derived from the one original virus back in early December 2019.

So one of the consequences of the fact that the virus just recently emerged in human populations is that nobody has an immunity to it, is that right?

Right now the entire world is naïve to this virus. We’ve never seen it before…. So once we’ve seen a virus we develop antibodies, and we develop what we call “memory cells” that produce antibodies. If we see those viruses again, our immune system kicks into gear really fast. Within days those cells multiply and produce antibodies against that virus or related viruses. But when you’re naïve it really takes 2 to 4 weeks to build a robust immune system and start to develop those antibodies. So people who get sick are not going to have a robust immune system right away. It’s going to take a few days or weeks to build that up.

What do you think the most important thing is for people to understand about this virus?

Your behavior can make a big difference, I think that is probably the most important think for people to understand. They shouldn’t feel helpless, they should understand that this is moving forward and the way we behave especially when it comes to quarantining, self-quarantining, social distance, hygiene, all those things are very important and it will affect the trajectory of this disease in our community.

Paul Keim, thank you so much for speaking with me today.

You bet.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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