What is Polio?
From: The Vaccine Education Center at the Children’s Hospital of Philadelphia
“Polio is caused by a virus. Three types of polio virus exist in nature. They are called wildtype 1, wildtype 2 and wildtype 3. Wildtype 2 was eradicated in 1999, and wildtype 3 was eradicated in 2020. Eradication means the virus no longer infects anyone anywhere in the world. Wildtype polio has been eradicated in all except two countries: Pakistan and Afghanistan. Unfortunately, some of the weakened viruses used in OPV mutated to become more infectious. These are called vaccine-derived polio viruses (VDPV). VDPV still cause outbreaks in some countries (see more in the section of this page, ‘If polio was eradicated from all but two countries, why are there still cases in other countries? ’).
Polio virus first replicates, or reproduces, in the intestines. Then it travels through the bloodstream where it can infect the brain and spinal cord. Polio virus causes paralysis when it replicates in and attacks the nervous system.
Polio virus is highly contagious and causes the same symptoms regardless of type. Polio affects people differently:
Some don't develop any symptoms. This occurs in about 72 of every 100 people.
Others have minor symptoms like sore throat, fever, tiredness, stomach pain, vomiting or constipation. This occurs in about 24 of every 100 people.
A small number develop meningitis, which is inflammation of the lining of the brain and spinal cord. When caused by polio, this is called nonparalytic polio. These individuals start with similar symptoms to those with mild illness. But one or two days later, they develop a stiff neck or back, vomiting, headache and pain. Illness lasts about two to 10 days, but these people typically recover completely. This version of polio occurs in about 4 of every 100 people.
Paralytic polio causes paralysis, muscle aches and spasms. Rates vary based on the type of polio causing the infection. Polio type 1 virus paralyzes about 1 in 200 people. Polio type 2 virus paralyzes about 1 in 2,000 people, and type 3 polio virus paralyzes about 1 in 1,000 people.
As those who survived polio infections as children have become older, another aspect of polio virus has become apparent. Some polio survivors experience symptoms similar to polio 15 to 40 years after their original recovery. The most common symptoms are muscle weakness and tiredness. This condition is known as post-polio syndrome. It’s estimated that about 25 to 40 of 100 polio survivors experience post-polio syndrome. Scientists are working to better understand what causes post-polio syndrome. Most of the evidence to date converges on roles for aging and long-term effects of the initial infection on the nervous system. Specifically, nerve cells that survived and compensated for the loss of neighboring nerve cells during the initial infection weaken or die as the polio survivor ages.”
Read the Complete Article:
Published with permission 2026