All epidemiologists agreed that flies could transmit polio to humans, Weaver wrote, but most believed DDT could not stop the disease. And while there was evidence that flies transmitted polio, he added, it was unlikely that they transmitted most cases.

What was the real cause of polio?

A virus called poliovirus causes polio. The virus enters the body through the mouth or nose, getting into the digestive and respiratory (breathing) systems. It multiplies in the throat and intestines. From there, it can enter the bloodstream.

How did polio get transmitted?

Poliovirus only infects people. It enters the body through the mouth and spreads through: Contact with the feces (poop) of an infected person. Droplets from a sneeze or cough of an infected person (less common).