History of Polio
Few diseases frightened parents more in the early part of the 20th century than polio did. Polio struck in the warm summer months, sweeping through towns in epidemics every few years. Though most people recovered quickly from polio, some suffered temporary or permanent paralysis and even death. Many polio survivors were disabled for life. They were a visible, painful reminder to society of the enormous toll this disease took on young lives.
Polio is the common name for poliomyelitis, which comes from the Greek words for grey and marrow, referring to the spinal cord, and the suffix –itis, meaning inflammation. Poliomyelitis, shortened, became polio. For a time, polio was called infantile paralysis, though it did not affect only the young.
Cause of Polio
Polio is caused by one of three types of poliovirus (which are members of the Enterovirus genus). These viruses spread through contact between people, by nasal and oral secretions, and by contact with contaminated feces. Poliovirus enters the body through the mouth, multiplying along the way to the digestive tract, where it further multiplies. In about 98% of cases, polio is a mild illness, with no symptoms or with viral-like symptoms. In paralytic polio, the virus leaves the digestive tract, enters the bloodstream, and then attacks nerve cells. Fewer than 1%-2% of people who contract polio become paralyzed. In severe cases, the throat and chest may be paralyzed. Death may result if the patient does not receive artificial breathing support.
History of Polio
It is likely that polio has plagued humans for thousands of years. An Egyptian carving from around 1400 BCE depicts a young man with a leg deformity similar to one caused by polio. Polio circulated in human populations at low levels and appeared to be a relatively uncommon disease for most of the 1800s.
Polio reached epidemic proportions in the early 1900s in countries with relatively high standards of living, at a time when other diseases such as diphtheria, typhoid, and tuberculosis were declining. Indeed, many scientists think that advances in hygiene paradoxically led to an increased incidence of polio. The theory is that in the past, infants were exposed to polio, mainly through contaminated water supplies, at a very young age. Infants’ immune systems, aided by maternal antibodies still circulating in their blood, could quickly defeat poliovirus and then develop lasting immunity to it. However, better sanitary conditions meant that exposure to polio was delayed until later in life, on average, when a child had lost maternal protection and was also more vulnerable to the most severe form of the disease.
Because of widespread vaccination, polio was eliminated from the Western Hemisphere in 1994. In 2016, it continues to circulate in just Afghanistan and Pakistan, with occasional spread to neighboring countries. Vigorous vaccination programs are being conducted to eliminate these last pockets. Polio vaccination is still recommended worldwide because of the risk of imported cases.
In the United States, children are recommended to receive the inactivated polio vaccine at 2 months and 4 months of age, and then twice more before entering elementary school.