Poliomyelitis is a contagious infection caused by the poliovirus, which is transmitted through contact with the fecal matter or saliva of an infected person. Once the virus enters the body through the gastrointestinal tract, it multiplies rapidly in the intestines.
Children under 5 years old are most susceptible to contracting the poliovirus because they often put potentially contaminated objects into their mouths. That’s why experts recommend that infants and young children start their vaccination regime as soon as possible.
Approximately 1 in 4 polio patients display flu-like symptoms for up to five days (before they clear up on their own). Common non-paralytic signs include:
- Sore throat
- Fever
- Fatigue or tiredness
- Headache
- Nausea
- Stomach pain
The virus can survive in the patient’s system for up to two weeks after symptoms first appear – making them highly contagious during this period. While more than 70 percent of infected individuals don’t show any signs of having it, they could still pass it on to others.
At its peak, polio was also referred to as infantile paralysis or “the crippler.” In severe cases, it’s capable of infecting the brain, nerves, and spinal cord, producing paralytic symptoms such as:
- Numbness or tingling (like a pins and needles sensation) in the limbs
- Paralysis of the limbs or intense muscle weakness, which could be fatal if it affects breathing muscles
- Meningitis, or infection of the brain and spinal column (another possibly fatal complication)
Other long-term medical issues, including post-polio syndrome, may cause persistent muscle pain, stiffness, or eventual paralysis.
Fortunately, international efforts to eradicate polio lowered the number of reported cases by more than 99 percent since 1988. Though rare, the poliovirus remains active in certain parts of the world with poor sanitation systems. The shortage of clean water to drink, cook with, or maintain personal hygiene encourages its transmission.
To this day, there’s still no cure for polio, but the vaccine is proving to be incredibly effective at preventing new outbreaks. No new natural cases in Europe or the Americas (where the polio vaccine is widely distributed) have been reported for several decades.
Before traveling to any regions where polio is still present (namely, Afghanistan and Pakistan), be sure to get up-to-date on all your vaccinations.
The polio history timeline begins with its initial outbreak and discovery by a British physician named Michael Underwood in 1789. He described the disease as a “debility of the lower extremities.” However, it wasn’t until 1840 that a German doctor, Jacob von Heine, theorized that the poliovirus was contagious.
The very first documented case of polio in America occurred in Rutland County, Vermont, shortly before the turn of the century. It eventually resulted in 18 deaths and 132 cases of permanent paralysis.
Two doctors in Austria, Karl Landsteiner and Erwin Popper, filtered out spinal cord fluid from a deceased polio patient and injected it into live monkeys. When the monkeys also developed polio, they confirmed the disease was in fact viral.
But it wasn’t until the invention of the electron microscope in the 1950s that the poliovirus would be readily accessible for in-depth study and analysis.
Once it was confirmed to be a viral infection, the medical community began working on the first polio vaccine to prevent its spread. Much of the early research and development took place in the United States.
Unfortunately, initial trials were poorly executed and caused great harm to those involved. Teams of researchers in New York and Philadelphia both administered vaccines containing active poliovirus to tens of thousands of living subjects, including children and chimpanzees. Many subjects became severely ill or paralyzed, experienced allergic reactions, and even died of polio.
Scientists in New York City grew the poliovirus in embryonic brain tissue, allowing them to study how the virus spread. However, they were reluctant to create a vaccine in this manner due to the risks associated with using nervous system tissues. This particular study did at least advance the medical community’s understanding of the poliovirus’ ability to multiply.
So when was the polio vaccine invented?
In the late 1940s, Dr. Hilary Koprowski of Lederle Laboratories in Philadelphia successfully administered a vaccine for type 2 poliovirus. He chose to test it on himself and his assistant after trying it on chimpanzees. They both drank the vaccine and observed no adverse effects.
Despite widespread concern over testing the vaccine on live human subjects, the studies continued. In the early 1950s, the National Foundation for Infantile Paralysis (now known as the March of Dimes) funded a study by Dr. Jonas Salk and his team of researchers. They planned to try three different strains of injectable, inactive-virus vaccines on humans.
When the U.S. Surgeon General questioned the safety of the trial vaccine, all polio vaccination programs were brought to a halt. An investigation revealed that it was responsible for 11 deaths, and hundreds of cases of paralysis. Apparently, some of the vaccines may not have been produced according to Salk’s methods and still contained active type 1 poliovirus.
Koprowski continued type 1 poliovirus vaccine trials in the former Democratic Republic of Congo, with some degree of success. But political and social unrest in the region prevented his team from conducting follow-up appointments with many of the test subjects.
For four years, researcher Albert Sabin partnered with health officials from the Soviet Union to produce a more affordable alternative. More than 10 million children received his oral polio vaccine (OPV) during this period.
Studies showed that Sabin’s version triggered a faster immune response and was easier to administer than Salk’s vaccine. Both Salk’s injectable vaccine and Sabin’s oral vaccine stopped the spread of all strains of the poliovirus through the bloodstream.
Ultimately, the U.S. Surgeon General recommended licensing of Sabin’s OPV, which combined vaccinations against all three types of polio in 1963.
In the decades that followed, widespread use of the polio vaccine finally began to stem the tide of this contagious disease. The World Health Organization would later launch a global poliovirus eradication program in the 80s.
Polio officially eradicated in the Americas (1994)
The Pan American Health Organization declared that wild poliovirus had been successfully eliminated in the Americas, thanks to extensive vaccination efforts. The World Health Organization proceeded to declare the Americas as the first region to achieve its goal of wiping out polio.
Salk polio vaccine reconsidered in the U.S. (1997)
Studies determined that since 1968, Sabin’s OPV vaccine had created 8 to 10 polio cases annually. The U.S. then chose to revise its immunization protocols to deliver only injection-based vaccinations (IPV) by the year 2000.
Poliomyelitis officially eradicated in Europe (2002)
The last reported case of polio on the European continent was a young Turkish boy in November 1998. In the summer of 2002, the World Health Organization declared that polio had also been eliminated in Europe.
Type 2 polio vaccine called into question (2016)
The global medical community switched from trivalent oral vaccines (covering types 1, 2, and 3) to a bivalent version (for types 1 and 3). This move helped curb vaccine-derived type 2 strains of polio, which had last been reported in 1999.
The history of polio is marked by great triumphs and tribulations. At this point, the disease has been almost completely wiped out across the globe. There were only 33 reported cases in 2018, representing a 99 percent drop over 30 years.
Until we reach 100 percent, polio can still spread rapidly amongst non-immunized individuals. Though unlikely, transmission of polio could result in up to 200,000 new cases worldwide if allowed to progress unchecked.
Polio vaccine history tells us that the only real cure is prevention. Be sure to speak with your child’s pediatrician or health care provider about their recommended vaccination schedule.