October 24 has been designated World Polio Day By the World Heath Organisation. Poliomyelitis /poʊlioʊmaɪəlaɪtɪs/, often called polio or infantile paralysis, is an acute, viral, infectious disease spread from person to person, primarily via the fecal-oral route. The term derives from the Ancient Greek poliós (πολιός), meaning “grey”, myelós (µυελός “marrow”), referring to the grey matter of the spinal cord, and the suffix -itis, which denotes inflammation., i.e., inflammation of the spinal cord’s grey matter, although a severe infection can extend into the brainstem and even higher structures, resulting in polioencephalitis, producing apnea that requires mechanical assistance such as an iron lung.
Although approximately 90% of polio infections cause no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream. In about 1% of cases, the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Different types of paralysis may occur, depending on the nerves involved. Spinal polio is the most common form, characterized by asymmetric paralysis that most often involves the legs. Bulbar polio leads to weakness of muscles innervated by cranial nerves. Bulbospinal polio is a combination of bulbar and spinal paralysis.
Poliomyelitis was first recognized as a distinct condition by Jakob Heine in 1840. Its causative agent, poliovirus, was identified in 1908 by Karl Landsteiner. Polio had existed for thousands of years in certain areas, with depictions of the disease in ancient art. Major polio epidemics started to appear in the late 19th century in Europe and soon afterwards in the United States, and it became one of the most dreaded childhood diseases of the 20th century. The epidemics are attributed to better sanitation which reduced the prevalence of the disease among young children who were more likely to be asymptomatic. Survivors then develop immunity. By 1910, much of the world experienced a dramatic increase in polio cases and epidemics became regular events, primarily in cities during the summer months. These epidemics—which left thousands of children and adults paralyzed—provided the impetus for a “Great Race” towards the development of a vaccine.
Developed in the 1950s, polio vaccines have reduced the global number of polio cases per year from many hundreds of thousands to under a thousand today. Enhanced vaccination efforts led by Rotary International, the World Health Organization, and UNICEF should result in global eradication of the disease, although in 2013 there were reports by the World Health Organization of new cases in Syria. On 5 May 2014, the World Health Organization (WHO) declared a public health emergency of international concern, or PHEIC, due to the renewed spread of polio – the outbreaks of the disease in Asia, Africa and the Middle East were considered “extraordinary”.The United States Center for Disease Control has recommended polio vaccination boosters for travellers and those who live in countries where the disease is occurring.