Cowpox refers to a disease that is caused by the cowpox or catpox virus.

The virus is a member of the orthopoxvirus family. Other viruses in this family include the smallpox and vaccinia viruses. Cowpox is a rare disease, and is mostly noteworthy as the basis of the formulation, over 200 years ago, of an injection by Edward Jenner that proved successful in curing smallpox.

The use of cowpox virus as a means of combating smallpox, which is a much more threatening disease to humans, has remained popular since the time of Jenner.

Once a relatively common malady in humans, cowpox is now confined mostly to small mammals in Europe and the United Kingdom. The last recorded case of a cow with cowpox was in the United Kingdom in 1978. Occasionally the disease is transmitted from these sources to human. But this is very rare. Indeed, only some 60 cases of human cowpox have been reported in the medical literature.

The natural reservoir for the cowpox virus is believed to be small woodland animals, such as voles and wood mice. Cats and cows, which can harbor the virus, are thought to be an accidental host, perhaps because of their contact with the voles or mice.

The cowpox virus, similar to the other orthopoxvirus, is best seen using the electron microscopic technique of negative staining. This technique reveals surface details. The cowpox virus is slightly oval in shape and has a very ridged-appearing surface.

Human infection with the cowpox virus is thought to require direct contact with an infected animal. The virus gains entry to the bloodstream through an open cut. In centuries past, farmers regularly exposed to dairy cattle could acquire the disease from hand milking the cows, for example. Cowpox is typically evident as pus-filled sores on the hands and face that subsequently turn black before fading away. While present, the lesions are extremely painful. There can be scars left at the site of the infection. In rare instances, the virus can become more widely disseminated through the body, resulting in death.

Both males and females are equally as likely to acquire cowpox. Similarly, there no racial group is any more susceptible to infection. There is a predilection towards acquiring the infection in youth less than 18 years of age. This may be because of a closer contact with animals such as cats by this age group, or because of lack of administration of smallpox vaccine.

Treatment for cowpox tends to be ensuring that the patient is as comfortable as possible while waiting for the infection to run its course. Sometimes, a physician may wish to drain the pus from the skin sores to prevent the spread of the infection further over the surface of the skin. In cases where symptoms are more severe, an immune globulin known as antivaccinia gamaglobulin may be used. This immunoglobulin is reactive against all viruses of the orthopoxvirus family. The use of this treatment needs to be evaluated carefully, as there can be side effects such as kidney damage. Antibodies to the vaccinia virus may also be injected into a patient, as these antibodies also confer protection against cowpox.