POXVIRUSES

Smallpox (variola)

This disease was eradicated in 1977 following an aggressive vaccination policy and careful detection of new cases coordinated by the World Health Organization. Its possible use in bioterrorism has resulted in the reintroduction of smallpox vaccination in some countries (p. 1031).

Monkeypox

This is a rare zoonosis that occurs in small villages in the tropical rainforests in several countries of western and central Africa. Its clinical effects, including a generalized vesicular rash, are indistinguishable from smallpox, but person-to-person transmission is unusual. Serological surveys indicate that several species of squirrel are likely to represent the animal reservoir.

Cowpox

Cowpox produces large vesicles which are classically on the hands in those in contact with infected cows. The lesions are associated with regional lymphadenitis and fever. Cowpox virus has been found in a range of species including domestic and wild cats, and the reservoir is thought to exist in a range of rodents.

Vaccinia virus

This is a laboratory virus and does not occur in nature in either humans or animals. Its origins are uncertain but it has been invaluable in its use as the vaccine to prevent smallpox. Vaccination is now not recommended except for laboratory personnel handling certain poxviruses for experimental purposes or in contingency planning to manage a deliberate release of smallpox virus. It is being assessed experimentally as a possible carrier for new vaccines.

Orf

This poxvirus causes contagious pustular dermatitis in sheep and hand lesions in humans