The Cowpox virus causes a skin disease known as cowpox. It is related to the vaccinia virus and gained its name because it spread by dairymaids touching the udders of infected cows. It manifests as red blisters. It is similar to smallpox although much milder and was actually the basis of the first smallpox vaccine. A person who recovers from cowpox is immune to smallpox.
In 1980 the World Health Organization announced that smallpox was the first disease to be eradicated world wide by a program of vaccination. Cowpox or CPXV has been restricted to the Old World where it mainly resides in wild rodents. The disease is usually spread to humans through domestic cats and rarely from rats. The virus usually remains localized although it can be deadly in immuno-suppressed patients.
From 1770 to 1790 six people tested the used of the cowpox vaccine as an immunization for smallpox in humans for the first time. One of these people scratched the fluid from the cowpox lesions into the skin of healthy individuals in order to immunize them. The virus is found throughout Europe and mainly in the UK. Symptoms amongst humans consist of pustular lesions found on the hands and wherever the virus was introduced. It is generally prevalent in late summer and fall and has an incubation period of nine to ten days.
The current vaccine for smallpox is so different from cowpox that it is considered a separate virus.