Why do some people think that there are many polio questions left waiting to be answered?

"But lost amidst the jubilation of Salk’s injected polio vaccine in 1955 and Sabin’s oral vaccine in 1961 is an intriguing riddle—a question whose answer is fascinating to those who are deeply curious about polio: What happened before the vaccine? What caused a previously innocuous virus to begin paralyzing people—seemingly randomly at first in the early 1800s, then more frequently in epidemic form in the late 1800s and early 1900s? For all the fanfare of victory over the dreaded disease, few seem interested in finding out why the vaccine was necessary at all."

The Moth in the Iron Lung: A Biography of Polio

The usual suspects...

The Many Myths for Polio Epidemics

The thing is, all of these are really just unanswered questions for anti-vaccine folks who are looking to push an agenda and trying to make you believe that vaccines don't work and aren't necessary.

Of course, the reality that vaccines are helping us get very close to eradicating polio, a disease with the nickname of 'The Crippler,' is getting in the way of the agenda.

“But is polio really an infectious and contagious disease?”

Turtles All The Way Down: Vaccine Science and Myth

So anti-vaccine influencers can push their own theories for what caused "polio" epidemics, including:

Arsenic, DDT, and lead poisoning
Other enteroviral infections
Undiagnosed congenital syphilis
Transverse myelitis and Guillain-Barré syndrome
Hand, foot, and mouth disease
Provocation of limb paralysis by intramuscular injections

Almost anything else except the polio virus which can be controlled, and eventually eradicated, with our polio vaccines.

Polio is a Disease of Development

What's the true story?

Polio is a disease of development!

What does that mean?

Well, once upon a time most everyone would get polio at a very young age, as infants.

But they didn't have many symptoms, and certainly didn't become paralyzed, because polio often has no symptoms or is very mild at this age.

As a society develops though, with improved hygiene and sanitation, that cycle of getting infected with polio as an infant gets interrupted.

"Before the developments associated with the 20th century, almost all children were exposed to poliovirus during infancy, largely due to poor sanitation conditions. Sewage entered watersheds without treatment transporting the polio virus into rivers, lakes, streams and thus direct into the water supplies. Indirectly, polio virus passed through the food chain and could be traced even in milk supplies. Due to the low case:infection ratio of infants, and due to protection from transplacentally acquired maternal antibodies, paralysis was rare amongst young children, although the disease itself was endemic. Because of their exposure to polio at an early age, infected infants acquired immunity to the disease thereby protecting them in later life.”

Modeling polio as a disease of development

And then when these children do eventually get exposed to polio, at an older age, they are at greater risk of getting paralytic polio.

That's a nice theory, but is there any proof that this happened?

“Serologic surveys, particularly those conducted by Paul and his associates (2, 6, 7), clearly showed that poliovirus infections were ubiquitous in the populations of developing countries where only infrequent sporadic cases of paralytic disease were seen (figure 2).”

The Epidemiology of Poliomyelitis: Enigmas Surrounding Its Appearance, Epidemicity, and Disappearance

Although anti-vaccine folks leave this out of their books that push the DDT theory of polio epidemics, not surprisingly, there is a lot of evidence for the theory of polio as a disease of development!

A lot of research has been done over the years to get answers to all of your questions about polio.

Children in Cairo were born with neutralizing polio antibodies which disappeared by the time they were about six months old. However, they were replaced by their own antibodies, indicating an infection while they still had some protection. Something not seen in Miami!

As expected, many studies have shown protective antibodies and low attack rates at young ages in less developed countries, with few cases of infantile paralysis.

Why would there be a difference in attack rates for two groups of people living in the same city?

This serologic evidence, with the recent modeling studies, clearly show that the polio virus caused paralytic polio, most likely as it became a disease of development.

But if polio became a disease of development, why did improved hygiene and sanitation help cholera and typhoid fever go away?

While a very good question, it is simply because unlike polio, you typically get cholera and typhoid fever from contaminated food and water. On the other hand, polio can also easily spread directly from person to person, even from those who don't have symptoms.

All Those Polio Questions Answered

Of course, the big unanswered question is why do these folks continue to push this kind of misinformation about polio?

Just consider all of their books and articles trying to connect DDT to polio...

In her book, Dissolving Illusions, Suzanne Humphries seems to make a good case connecting DDT and polio. She even has a nice graph!

A lot of work has been done over the years to debunk polio myths by anti-vaccine influencers.

Her graph isn't accurate though - the peak year for production of DDT was in 1963.

The only problem is that it is just an illusion - pure propaganda.

To force a correlation with polio cases, she uses pesticide production, instead of pesticide use. But even then, her numbers aren't even accurate!

The peak year for use of DDT in the United States was in 1959, well after polio cases and deaths peaked. DDT use does not correlate with polio cases.

Wait, how could we have produced more pesticides, like DDT, than we used? A lot of it was exported for use in other countries.

But again, data from the EPA shows that pesticide production does not match the data on Suzanne Humphries' graph.

"The evidence to date, gathered from several types of studies, favors the former possibility. Thus Trask and Paul and Melnick by examining sewage from a certain area in New York City, monthly for six years, found that virus, presumably derived from the only known reservoir, man, could be isolated fairly regularly from sewage samples in the late summer and early fall but not during the rest of the year."

The Epidemiology and Pathogenesis of Poliomyelitis

Still, even if it was DDT, why did they find the polio virus in sewage samples during times of epidemics?

"Popper and Landsteiner deduced the viral nature of polio by carefully filtering preparations of spinal cord fluid from a person who had died of polio. The filters were known to trap bacteria. When Popper and Landsteiner injected the filtered preparations into monkeys, the monkeys developed polio. The researchers then concluded that an infectious particle smaller than bacteria caused the disease."

Polio Timeline - History of Vaccines

And if it was DDT, how did monkeys develop symptoms of polio after being injected with spinal cord fluid of people who had polio?

Not convinced yet?

What about the idea that they simply changed the diagnostic criteria for polio after 1954?

"The practice among doctors before 1954 was to diagnose all patients who experienced even short-term paralysis (24 hours) with “polio.” In 1955, the year the Salk vaccine was released, the diagnostic criteria became much more stringent."

Dissolving Illusions

The diagnostic criteria was indeed changed - it changed in 1955 to include residual paralysis 10 to 20 days after onset of illness and again 50 to 70 days after onset.

Did we change the diagnostic criteria again in the late 1980s or are we seeing the effect of polio vaccines and the 1988 resolution to eradicate polio?

But that didn't make polio go away!

Polio also didn't go away because we simply renamed it to acute flaccid paralysis.

Hopefully our explanations will help much of the misinformation about polio go away though!

All Your Polio Questions Answered

The Many Myths for Polio Epidemics

Polio is a Disease of Development

All Those Polio Questions Answered

More on Polio Myths