Efforts to Eradicate Polio Worldwide

Micaela Martinez, PhD, postdoctoral fellow in the Department of Ecology and Evolutionary Biology at Princeton University, discusses how the poliovirus has not yet been eradicated despite preventive measures and deadlines.

Interview Transcript (slightly modified for readability)

“Polio is a disease that is characterized by paralysis. When we think of polio, we think of the classic symptoms of the disease, which is acute flaccid paralysis; this is paralysis usually seen in a limb. Polio was an emerging epidemic disease in the early 1900s across most of the industrialized world. The, in the 1950s/early 1960s, two vaccines against polio were developed: there’s a vaccine developed by Jonas Salk, known as IPV, the inactivated polio vaccine; and then there’s the Sabin vaccine, developed by Albert Sabin, and this known as OPV, the oral polio vaccine. These vaccines were used to eliminate polio, eradicate polio, from the Americas. I should make the distinction between elimination and eradication. The eradication of a disease is when you drive a pathogen to extinction; so, it’s gone, you’ve gotten rid of every single infection in the population. Elimination is when we reduce the disease below some threshold. The goal for polio is to eradicate it, drive this virus to extinction worldwide.

This was very successful in the Americas very early on, and so in the late 1980s, global polio eradication became a goal. This was following [on] the heels of smallpox. The goal has been [to] get rid of this virus everywhere and that’s proved to be very difficult. Over the years, there have been many goals set for deadlines for when polio eradication would happen and each time one of those deadlines rolls around, it doesn’t happen. The most recent of those deadlines was in 2014 and at the time there were three countries [where polio was] still endemic, meaning that there was still active transmission of this virus. Those were Pakistan, Afghanistan, and Nigeria. Nigeria has had some recent success, but Pakistan and Afghanistan still have polio and in both of those countries, the majority of the countries are polio-free, they don’t have ongoing transmission. But, there are these polio strongholds, small regions of each of those countries where vaccine workers just aren’t able to get in and get every child. Pakistan has particularly been a problem; there’s been violence against polio workers, so individuals who are going out and trying to give OPV, the Sabin vaccine, [are] being killed, and so that has meant that kids are not able to get this vaccine and that these strongholds still exist. It is because of those social and political aspects [that] we are not able to get to every child and the 2014 deadline for stopping polio transmission has passed.

We’ve had 19 paralytic cases this year. When we say 19 that sounds like a very small number, but those are the number of individuals [who] have actually shown up paralyzed by polio, but in fact, that means there are many, many more individuals [who] are infected with it because only about one in every hundred to two hundred infected individuals actually show up with paralysis. So, the virus is still out there. Throughout my PhD I thought, ‘It’s going to get eradicated. It’s going to get eradicated,’ and we still don’t know when it will actually happen.”