Badge-wearing members of the pro-vax brigade will often cite Polio as an example of the effectiveness of vaccines yet seem to completely ignore the contribution of ENGINEERS who helped improve water systems - which lead to a significant drop in "Polio cases" before any miracle vaccine was introduced. If you read about the history of sanitation prior to 1950 - then it becomes apparent that people were ignorant of hygiene at the time and it used to be the norm for people to dump sewage in the streets. It is therefore no surprise that people exposed to sewage-contaminated water would become ill. There are multiple studies that discuss a reemergence of Polio in areas that do not have access to clean water.
Here is a quote from a 1948 article from a New Zealand newspaper titled 'Greater Intensity Of Wellington Polio Gases' that shows that the symptoms being observed at the time were caused by exposure to pollution.
Quote: "Discussing the approaching bathing season today, the medical officer of health (Dr L. S. Davis) said that while there was no prohibition of bathing, he could not say that the water was safe".
"Our reports,” he added, “indicate that the harbor is polluted by the daily discharge of sewage.”
Instead of attributing the sickness to the toxins in the sewage they blame it on a virus. The default position in virology is that all disease is caused by a virus until proven otherwise.
Hence Scurvy, Beri-beri, Pellagra and even Cancer were blamed on viruses until it was proven without any shadow of a doubt that these disease states had another cause.
Source: Greater Intensity Of Wellington Polio Gases
Northern Advocate, 22 September, 1948, pp.6.