Only one human disease in history has been fully stamped out; smallpox, with the World Health Organization declaring it eradicated way back in 1980.

But polio could be next.

Yes, the disease that brings up imagery of wheelchairs and iron lungs might soon be on its way out, but we’re not there quite yet.

Polio, also known as poliomyelitis, is an infectious disease caused by the aptly named poliovirus, which comes in three strains, and is spread mostly by consuming contaminated water.

Polio can be passed through the air with oral fluids, like from a cough or a sneeze, but the cycle today usually begins with fecal oral transmission, mostly in areas with poor sanitation.

Those infected with the poliovirus can experience no symptoms, but people can experience fatigue, fever, muscle weakness, loss of muscle, headaches, nausea, and more. Polio’s most severe form can lead to paralysis, weakened lungs, and, sometimes, death.

On this episode of SICK, we talk with Jay Wenger, Director of Polio at the Bill & Melinda Gates Foundation, about the infectious disease, how it spreads, its symptoms, and the ongoing eradication efforts.