When I was young, many years ago, my parents did not allow my brother or me to go swimming at our local pool because it was thought to be the source of infantile paralysis. (Infantile paralysis is an old synonym for poliomyelitis, an acute and devastating viral disease.)  

My parents were not alone. It was common knowledge that children could be exposed to the virus there. Later a study conducted in 1946 showed that chlorine was actually one of the few known chemicals that could inactivate the virus.

Poliomyelitis had been frightening the country beginning in the early 1900s and continued until the polio vaccine was developed. (It is derived from polios, meaning gray, and myelitis, indicating inflammation of the spinal cord.)

The first major documented polio outbreak in the United States occurred in Rutland County, Vt., in 1894. Eighteen deaths and 132 cases of permanent paralysis were reported. Charles Caverly, M.D., noted the appearance of acute nervous system disease and was one of the first physicians to recognize that polio could occur with or without paralysis. The contagious nature of the disease was established in 1905.

Beginning from about 1916, a polio epidemic appeared in at least one part of the country, with the most serious cases reported in the 1940s and ’50s. In the epidemic of 1949, 2,720 deaths from the disease occurred in the United States and 42,173 cases were reported.

Polio is a debilitating virus (poliomyelitis) that has struck fear in the hearts of parents for centuries. It causes severe muscle weakness and paralysis, often affecting the spinal cord, difficulty breathing and sometimes death.

The virus is typically contracted by ingestion, usually when the individual’s hands have been exposed to the feces of someone who is infected and subsequent swallowing of the virus. Polio is very contagious and spreads through person-to-person contact through droplets from a sneeze or cough. An infected person may spread the virus to others immediately before and one to two weeks after symptoms occur.

The virus can live in an infected person's feces for many weeks and can contaminate food and water in unsanitary conditions. It thrives in areas where living conditions are unclean and hygiene is poor.

Man is the only source for poliovirus. The virus enters the mouth and multiplies in lymphoid tissues in the pharynx and intestines.

 What appears to be the polio virus can be traced back to 1580 B.C. Egyptian carvings and paintings show people with withered limbs walking with canes. These people appear to be healthy other than their affected limbs. They also show young children walking with the aid of canes. While the virus does affect adults, it is more common in young children and infants. When it infects an older individual such as an older child, teenager or adult, the chances of paralysis and severity of the effects of the virus are much more common.

There are three types of polio viruses: types 1, 2 and 3. Type 1 is the most virulent and common.

The world is indeed fortunate following the introduction of a vaccine designed to prevent polio. Jonas Salk became a national hero when he allayed the fear of the dreaded disease following approval of his injectable vaccine in 1955. Although it was the first, it was not be the last; Albert Sabin introduced an oral vaccine in the 1960s that replaced Salk's. The Salk and Sabin vaccines are trivalent, that is active against all three virus types.

In 1988, the World Health Organization (WHO) set its sights on eradicating polio. This came after success against smallpox. Since then, the incidence of polio has decreased from an estimated 350,000 annual cases to 1,315 in 2007. Indigenous type1 and type 3 have been eliminated worldwide from all but four countries (Afghanistan, India, Nigeria and Pakistan). It was thought that type 2 had been eradicated, but just last year type 2 vaccine-derived virus is still circulating and last year caused polio in Syria and the Democratic Republic of Congo. This year cases emerged in Nigeria, Niger and Somalia. Health officials worry that outbreaks in Somalia, in particular, may spread to neighboring countries. This is a setback for Africa.

The last person on the continent paralyzed by the wild polio virus was a Nigerian child who contracted the disease in 2016. In 2017, cases caused by vaccine-derived viruses overtook, for the first time, those caused by the wild version. They are still rare, but attracting more notice than those caused by the wild virus.

Fortunately, thanks to the vaccines, the United States has been polio-free since 1979, but it is still a threat in other countries and requires all of us to be vaccinated on schedule. People most at risk are those who never have been vaccinated, those who never receive all the recommended vaccine doses, and those traveling to areas that could put them at risk of acquiring polio. Unfortunately, there is a growing number of countries with cases of the disease caused by the vaccine.

Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, will touch on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at maxsherman339@gmail.com.