THE HISTORY OF POLIO

The Disease
Poliomyelitis has been known at least since Antiquity. An ancient Egyptian stele, for example, shows an apparently healthy man with a withered leg thought to be the result of polio (see the photograph at the top of this page). The Roman emperor Claudius walked with a limp which is also believed to have been an after-effect of polio. The first clinical description of the disease was written in Great Britain by physician Michael Underwood in 1789. It came to be known as "Heine-Medin diseas" when the first medical report of polio by Jakob Heine (1840) was followed by the first empirical study of it by Karl Oskar Medin (1890). Because epidemics primarily struck children, polio was also called "infantile paralysis".

Until the end of the 19th century, polio most often affected children from 6 months to 4 years of age. Infection at an early age generally left the victims with light consequences and permanent immunity to reinfection. Ironically, improved sanitation in cities in the 20th century led to fewer exposures to the polio virus and, therefore, fewer opportunities to become immune to it. This led to victims being struck in later childhood and even early adulthood, and to victims being more strongly affected by the disease. Rates of paralysis and death from the disease greatly increased. Coming to a peak in the early 1950s, the death rate from polio reached 5% and the paralysis rate climbed to 37%.

The Iron Lung
The iron lung was invented at Harvard University and tested at the Boston Children's Hospital in 1928. This bulky device in which a polio victim was placed during acute infection (see photograph at the top of this page) worked by changing the air pressure inside the chamber. This forced lungs to breathe when they were too weakened by the infection to function on their own. Though it saved thousands of lives, the iron lung was neither a preventative nor a cure for polio.

The Salk Vaccine
The first attempt to create a polio vaccine was made in 1935 by Maurice Brodie at New York University. He used the virus found in monkey spinal cords, but this did not lead to immunity in humans.  In the early 1950s, a group of researchers at the Boston Children‚s Hospital grew the polio virus in human tissue. This breakthrough led to the successful development of the polio vaccine by Jonas Salk at the University of Pittsburgh in 1952. The Salk vaccine proved to be up to 70% effective against poliovirus type 1, more than 90% effective against poliovirus types 2 and 3, and against bulbar polio. Mass immunization campaigns followed (see photograph at the top of this page) and the rate of polio infection in industrialized countries dropped dramatically. By 1994, polio was entirely eradicated from the Americas and it was eliminated from Europe in 2002.

Polio in the World Today
The United Nations, through UNICEF and the World Health Organization, began a global programme to eradicate polio in 1988. Within 20 years this effort led to a 99% reduction in annual cases, putting poliomyelitis on the path to becoming only the second disease to be completely eradicated (the first being smallpox in 1979). Polio is now prevalent only in Afghanistan, Pakistan, India and Nigeria where civil strife and a limited health system have hindered distribution of the vaccine.