Poliomyelitis is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route. Although around 90% of polio infections have no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream. In fewer than 1% of cases the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Spinal polio is the most common form, characterized by asymmetric paralysis that most often involves the legs. 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 quietly as an endemic pathogen until the 1880s, when major epidemics began to occur in Europe; soon after, widespread epidemics appeared in the United States. These epidemics—which left thousands of children and adults paralyzed—provided the impetus for a "Great Race" towards the development of a vaccine. The polio vaccines developed by Jonas Salk in 1952 and Albert Sabin in 1962 are credited with reducing the annual number of polio cases from many hundreds of thousands to around a thousand. Enhanced vaccination efforts led by the World Health Organization, UNICEF and Rotary International could result in global eradication of the disease. (more...)

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• At least 60 people die following twin suicide bombings outside the Pakistan Ordnance Factories in Wah, Pakistan.
• Spanair Flight 5022 crashes immediately after takeoff from Barajas Airport in Madrid, Spain, killing at least 150 people on board.
• Usain Bolt (pictured) of Jamaica wins gold medals in the 100-metre and 200-metre sprints at the 2008 Summer Olympics, setting new world records of 9.69 and 19.30 seconds, respectively.
• President of Zambia Levy Mwanawasa dies after suffering a stroke in late June.
• Facing impeachment, Pervez Musharraf announces his resignation as President of Pakistan.
• Michael Phelps wins his eighth gold medal of the 2008 Summer Olympics, surpassing Mark Spitz's record for most gold medals won at a single Olympics.
• Maoist leader Prachanda is elected Prime Minister of Nepal, the first since the country's transition from a monarchy to a republic.
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August 22: Feast Day of the Immaculate Heart of Mary (Roman Catholic Church)

• 1485 – Lancastrian forces under Henry Tudor, Earl of Richmond defeated Yorkist forces under Richard III of England at the Battle of Bosworth Field, decisively ending the Wars of the Roses.
• 1791 – A slave rebellion erupted in the French colony of Saint-Domingue, starting the Haitian Revolution.
• 1864 – The Red Cross movement led by Henry Dunant (pictured) officially began when twelve European nations signed the First Geneva Convention, establishing the International Committee of the Red Cross.
• 1910 – Korea was annexed by Japan with the signing of the Japan-Korea Annexation Treaty, beginning a period of Japanese rule of Korea that lasted until the end of World War II.
• 1922 – Irish Civil War: Irish National Army commander-in-chief Michael Collins was assassinated in an ambush while en route through County Cork at the village of Béal na mBláth.

• More events: August 21 – August 22 – August 23

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