For those with trouble breathing, an iron lung was the preferred treatment during the height of the 20th century polio epidemic. An iron lung was a machine that literally pushed and pulled the muscles in the chest, manually working the lungs so that they could take in air and exhale it. While many patients only had to be in iron lungs for a little while, a few weeks or months at most, others had to stay in them for years, sometimes for their whole lives. And, while production of new iron lungs ended in the early 1990s, there are still about two hundred iron lungs that still exist ("Iron Lung", 2005). There are also some people in the world who still live inside iron lungs, even today, sometimes having been inside them for decades already.

             Polio is contracted from contact with the polio virus. Such contact happens via person-to-person transmission, normally either orally or through contact with contaminated fecal matter. The polio virus invades the gastrointestinal tract of the person it is infecting. The person can then transmit the virus to others through secretions from the nose and mouth during the acute phase of the disease, and then through fecal matter for several weeks after this. Generally, a person's body will produce effective antibodies to the polio virus, thus preventing the virus from leaving the gastro-intestinal tract (Black, 1996). However, in a small number of cases, the virus does penetrate the gastrointestinal tract, and this is when the danger for developing paralytic polio appears. .

             Because most cases of polio are asymptomatic, the virus can circulate among a population for some time before it is known that there is polio in the community. While those who exhibit no symptoms may not be aware they are infected, they can still carry and transmit the virus to others, who may then develop symptoms themselves. If a person does develop some sort of symptoms, whether paralytic or not, then at least the period of contagion can be estimated; polio is generally most contagious in the ten days before and after symptoms occur.