Shingles occurs in adults and is believed to be a recurrence of infection by the virus that causes chickenpox. Presumably, the virus has remained latent in ganglia of the nervous system until it is reactivated. The disease is characterized by painful lesions surrounding the body trunk. The disease is highly contagious. Acyclovir may be recommended for therapy. Smallpox. Smallpox is a viral disease caused by a large, boxlike, DNA-containing virus having a complex shape. At one time, smallpox was a major cause of death in the world. It was accompanied by pus-filled lesions covering the body surface, and usually it resulted in death. Immunity was rendered by an injection of cowpox (vaccinia) viruses, as first recommended by Edward Jenner in 1798. Smallpox has apparently been eradicated on the earth and has not appeared in humans since October 26, 1977. It is the first infectious disease ever to be eradicated.
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