Polio (also known as poliomyelitis or infantile paralysis) is an illness caused by poliovirus. At one time, poliovirus infection occurred throughout the world.
The history of polio begins with records from antiquity mentioning crippling diseases compatible with polio. Michael Underwood first described a debility of the lower extremities in children that was recognizable as poliomyelitis in England in 1789. The first polio outbreaks in Europe were reported in the early 19th century, and polio outbreaks were first reported in the United States in 1843.
For the next hundred years, epidemics of polio disease were reported from developed countries in the Northern Hemisphere each summer and fall. These epidemics became increasingly severe, and the average age of people affected rose. The increasingly older age of people with primary polio infection increased both the severity of the disease and number of deaths from polio. In 1952, polio reached a peak in the United States, with more than 21,000 cases of paralytic polio.
In the immediate pre-vaccine era, improved sanitation allowed less frequent exposure and increased the age of primary infection. Boosting of immunity from natural exposure became more infrequent, and the number of susceptible people increased, which ultimately resulted in the occurrence of polio epidemics, with 13,000 to 20,000 paralytic cases reported annually.
Polio's history changed following the licensing of a polio vaccine. In the early vaccine era, the incidence of polio dramatically decreased after the introduction of inactivated polio vaccine (IPV) in 1955. The decline continued following oral polio vaccine (OPV) introduction in 1961. In 1960, a total of 2,525 paralytic cases were reported, compared with 61 in 1965.
The last cases of paralytic poliomyelitis caused by endemic polio transmission of wild virus in the United States were in 1979, when an outbreak occurred among the Amish in several Midwest states. The virus was imported from the Netherlands.
Vaccine-Associated Paralytic Polio
From 1980 through 1999, a total of 152 confirmed cases of paralytic poliomyelitis were reported in the United States (an average of eight cases per year). Six cases were acquired outside the United States and imported. The last imported case was reported in 1993.
Two cases were classified as indeterminate (no poliovirus isolated from samples obtained from the patients, and patients had no history of recent vaccination or direct contact with a vaccine recipient). The remaining 144 (95 percent) cases were vaccine-associated paralytic polio caused by live oral polio vaccine.
In order to eliminate vaccine-associated paralytic polio from the United States, it was recommended in 2000 that inactivated polio vaccine be used exclusively in the United States. The last case of vaccine-associated paralytic polio acquired in the United States was reported in 1999.
In 1985, the member countries of the Pan American Health Organization adopted the goal of eliminating poliomyelitis from the Western Hemisphere by 1990. The strategy to achieve this goal included:
- Increasing polio vaccination coverage
- Enhancing surveillance for suspected cases (i.e., surveillance for acute flaccid paralysis)
- Using supplemental immunization strategies such as national immunization days, house-to-house vaccination, and containment activities.
Since 1991, when the last wild-virus-associated indigenous case was reported from Peru, no additional cases of poliomyelitis have been confirmed despite intensive surveillance. In September 1994, an international commission certified the Western Hemisphere to be free of indigenous wild poliovirus. The commission based its judgment on detailed reports from national certification commissions that had been convened in every country in the region.
In 1988, the World Health Assembly (the governing body of the World Health Organization [WHO]) adopted the goal of global eradication of poliovirus by the year 2000. Although this goal was not achieved, substantial progress has been made. One type of poliovirus appears to have already been eradicated. The last isolation of type 2 virus was in India in October 1999. Furthermore, in 2003, only 784 confirmed cases of polio were reported globally, and polio was endemic in six countries.
The polio eradication initiative is supported by a coalition of international organizations that includes WHO, the United Nations Children's Fund (UNICEF), and other bilateral and multilateral organizations. Rotary International has contributed more than $500 million to support the eradication initiative and global polio eradication may be achieved within the next decade.
Post Polio Litaff, Association A.C _APPLAC Mexico
