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Polio has existed since ancient times and was documented in the written record in the 18th and 19th centuries, causing paralysis and death. There are 3 wild types of polio virus (types 1-3). There were serious outbreaks in Europe and the United States in the early 20th century, compelling scientists to try and find a vaccine. Although polio has no cure, as you will read in this timeline, vaccines have successfully eradicated polio in the western hemisphere since 1994.
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