The word polio comes from Greek meaning “gray”. The word “myelitis” means inflammation of the spinal cord or the bone marrow. Thus the word poliomyelitis means the inflammation of the spinal cord (gray matter). Polio is an acute, contagious viral disease that attacks the central nervous system, injuring or destroying the nerve cells that control muscles and sometimes causing paralysis. Another name is infantile paralysis.

Polio has been around for centuries, but first described by an Englishman in 1789. The first outbreaks were reported in Europe in the 19th century with the US following several years later in 1843. Over the years the epidemics became increasingly severe and the average age of persons affected rose. The epidemics would usually occur in the summer and early autumn. The US peaked in 1952 with over 21,000 paralytic cases. Polio cases fell rapidly following the introduction of polio vaccine. The last case in the US was in 1978.

Poliovirus is a member of the enterovirus subgroup and consists of three different serotype types. They are transient inhabitants of the gastrointestinal tract. The virus enters the mouth, multiplies in the throat, GI tract and the lymphatic system, then goes to the central nervous system, spreading along nerve fibers and destroying the nerve cells that control muscles sometimes causing paralysis. Most often affected are the leg muscles but can affect any muscle including those that control breathing and swallowing (this is where the iron lung was used). Polio occurs only in humans.

Polio is a very serious disease, but not often fatal. Infection is more common in infants and young children and occurs at an earlier age among children living in poor hygienic conditions. The risk of paralysis after infection increases with age. Many infections are asymptomatic. A person infected with poliovirus is most infectious from 7 to 10 days before and after onset of symptoms but the virus may be present in the stool for 3-6 weeks. There is no cure for polio but receiving the vaccine cuts down the chances that one will become infected.

Dr. Jonas Salk developed the first safe vaccine in 1952. It is sometimes known as the “Salk Vaccine”. This was a killed virus and was replaced with a live virus (oral) in 1961 with the 3 serotype of the poliovirus present. This was then replaced with a killed virus (inactivated). The last vaccine associated paralytic polio (VAPP) caused by live oral vaccine was in 1999. Oral polio (OPV) is the vaccine of choice for global eradication. OPV is no longer used in the US since Jan. 1, 2000. However, if there were an outbreak of paralytic polio, OPV would remain a public option.

The American Academy of Pediatrics recommends a 4-dose, all IPV, vaccine schedule for all routine immunizations for all infants and children. The first dose starts at 2 months, then at 4 and 6 months, with a booster at 4-6 years prior to entering school.

Polio is one of those diseases that decreased dramatically after the introduction of the polio vaccine. The disease is still present in the world, but in order to keep the US disease free, we need to maintain high levels of polio immunizations in our country.