Cowpox

Cowpox is a skin infection caused by the cowpox virus, an orthopoxvirus closely related to vaccinia. It produces large painful blisters, usually on the hands and face, with fever and swollen glands. The disease was first seen in dairy workers who handled the udders of infected cows, but woodland rodents, especially voles, are the true reservoir, and most human cases in Europe today come from domestic cats. It is a zoonosis, passing between species, and it is much milder than smallpox. Its importance is historical: the observation that milkmaids who had caught cowpox seemed protected from smallpox led Edward Jenner to publish his account of the disease in 1798 and to develop vaccination, the method that later helped the World Health Organization declare smallpox eradicated in 1980.