A video this dense with information makes me all the more respectful of public health scientists. We fight all kinds of different viruses, and each has their own story. Today we learn how many different types of polio virus there are. There's the wild virus, which has three main variants. And then each of those variants can be a wild virus, deactivated virus, attenuated virus, or a mutant virus. We use some of these to fight the others.
Before we had vaccines, polio was super virulent because most infected people weren't even aware they had the virus, so they constantly spread it to others who might not be so lucky. A small fraction of the infected got sick, and were in danger of dying or becoming permanently disabled. The only real solution is to vaccinate the entire population and wipe polio viruses from the face of the earth, like we did with smallpox.