Cowpox is a contagious viral disease of cows. It is characterized by small pustules (pus-filled bumps) on the skin, especially on the cows’ udders and teats. Cowpox can be passed on to human beings, though for people it is a minor disease that causes a few sores on the hands. Cowpox helped Edward Jenner, a British physician, discover vaccination as a means of preventing smallpox, an extremely contagious disease among people.
Many people believed that anyone who had caught cowpox could not catch smallpox. In 1796, Jenner took matter from the hand of a dairymaid who had become infected with cowpox while milking the cows. He then inserted the matter into the arm of a healthy 8-year-old boy. When Jenner later introduced smallpox matter into the boy’s arm, it had no effect, because the boy had been vaccinated with cowpox matter.
See Jenner, Edward; Smallpox.
