• Cowpox virus is only found in Eurasia. Most reports of cowpox virus elsewhere in the world refer to vaccinia virus (the smallpox vaccine) which, when human vaccination was widespread, occasionally escaped into domestic stock.
• Cowpox virus has a very wide host range which includes cattle, man, domestic cats and various zoo animals ( See Picture ). However, the reservoir host is wild rodents. Antibody to cowpox virus is found in wild voles and woodmice in Western Europe, and virus has been isolated from other rodents in Eastern Europe and Eurasia.
• Bovine cowpox is very rare (unlike infection with pseudocowpox virus which is enzootic in cattle world-wide.) Cowpox virus causes teat lesions in cattle, and may spread rapidly through the herd on milking equipment. Cattle to man transmission can occur, but most people with cowpox have had no contact with cattle.
• The most commonly recognised host of cowpox virus is the domestic cat. About one-half of human cases in the UK can be traced to contact with an infected cat.
• Cats probably become infected when hunting.
• Most affected cats are adult and come from rural environments, and almost all are known by their owners to hunt small mammals.
• Most feline cases are seen in the autumn ( See Picture ), probably because small mammal populations are at their maximum size and because individual rodents are most active and therefore are most prone to capture at that time of year.
• Cat-to-cat transmission can occur, but generally causes only asymptomatic infection in the recipient cat.
• Cowpox virus has also been isolated from exotic cats, including cheetahs, lions, pumas, ocelots and lynx in European zoos, and also from okapi, elephants, rhinoceroses, and anteaters.

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