Until the middle of the 20th century, polio affected people all over the world. The disease, caused by a virus in the genus Enterovirus, often left its survivors with weakened muscles or varying degrees of paralysis. In their later years, many once-healthy survivors experienced a condition known as post-polio syndrome. Once effective vaccines were developed, polio was eradicated in the United States and other countries, although it still remains a threat in many developing areas. This revised edition of ""Polio"" contains new illustrations and updated coverage of all aspects of this disease, including the latest vaccination information, world outbreak and immunization statistics, and a progress report on international efforts to eradicate polio.The chapters include: The History of Polio; The Transmission of Polio and How It Affects the Body;Vaccines and How They Work; Just When We Thought It Was Safe: Post-Polio SyndromeWhat Lies Ahead? And, The Future of Polio.