Understanding the Natural Ecology of Polio Can Help Drive Eradication

Micaela Martinez, PhD, postdoctoral fellow in the Department of Ecology and Evolutionary Biology at Princeton University, explains how studying polio in the absence of intervention can provide insight into how to eradicate the disease.

Interview Transcript (slightly modified for readability)

“As an ecologist, of course I’m interested in the ecology of pathogens, but I would say that it’s extremely important to know your enemy and so with polio we’re wanting to drive this pathogen to extinction. We need to know how it persists, how it’s been able to be maintained in human populations so that we can essentially figure out where it’s most vulnerable and how to get at it.

Many ecologists, conservation ecologists, are in the business of keeping species from going extinct and so, in ecology, we have tools to know how to keep species around. I essentially do the flip side of that, which is [asking the question of], can we use that same information to know how to drive something to extinction? That’s what I’ve done in terms of polio.

We want to do this in the absence of intervention because if you know the natural ecology of a species or of a pathogen, then you can say, ‘Okay, I know how this game plays out without any intervention, so then how can I come in with the tools that I have and very effectively hit that pathogen hard with vaccines?’

In addition to that, the other reason why it’s important to study a disease like polio in the absence of intervention is a pure numbers game. Right now we vaccinate against polio very heavily; most of the world is polio-free. That means that there are very, very few cases of polio. Now, if you want to understand how a virus is transmitted, you need to be able to see, or at least infer, these chains of transmission, how this pathogen moves from person to person to person to person. If you have very few cases, there are just too few numbers to work with.

What we can do and what I’ve shown in some of my work is, we can look back in time [to] when we had a lot of polio. Times like in the United States when we would have over 50,000 children paralyzed by this virus in a summer. We can go back, take those numbers, and then let those numbers tell us about how this virus moves around in a population, how it persists on a really large special scale. Then we can take that ecology and apply it to the current context because we just can’t get the underlying ecology out of the data that exists today because the numbers are just too few and far between.”