The Epidemiology of Smallpox
Smallpox is caused by a virus which is transmitted only between humans. There is no known reservoir for the disease among other species of animals.2 Consequently, if an isolated region is smallpox free, the only way for the disease to occur is by importation. Specifically, someone susceptible to smallpox must contract it in a region where the disease is found and then travel to the smallpox free region. Unfortunately, as with most viral diseases, there is a period of time between initial infection and the appearance of externally observable symptoms. As a result, an infected individual can innocently transmit the disease to susceptible individuals before the disease is identified.
KeywordsInfected Individual Public Health Authority Secondary Case Smallpox Vaccination Isolation Facility
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