Photo Illustration by The Daily Beast
By Marisa Eisenberg, Associate Professor of Complex Systems, Epidemiology, and Mathematics, University of Michigan; Andrew Brouwer, Research Investigator in Epidemiology, University of Michigan; and Joseph Eisenberg, Professor and Chair of Epidemiology, University of Michigan
The world is at the brink of eradicating polio. Only three countries now have ongoing transmission: Nigeria, Afghanistan and Pakistan. And in 2017, there were only a couple dozen cases of paralytic wild polio reported worldwide—a massive fall from the estimated 350,000 cases reported across 125 countries in 1988. Development of the polio vaccine and global vaccination efforts are at the heart of this monumental public health achievement.
Epidemiologists typically detect polio transmission based on reported cases of acute flaccid paralysis (AFP). The World Health Organization certifies a country as polio-free if there are no reports of AFP for three years. But AFP is a severe outcome that occurs in a very small fraction of polio infections. It’s just the tip of the iceberg—one case of AFP indicates substantial underlying polio transmission in a population.