Poxviruses belong to family Poxviridae and are among the complex viruses in the field of virology. The disease has a great historical impact; the first case of the poxvirus was reported about 2000 years ago in China. The virus produces a characteristic pock like lesions in the body (small pox). Last naturally occurring outbreak was reported in Somalia in 1977.

What characteristics of small pox made its eradication possible?

• •  Short incubation period

•  No animal reservoir

•  High morbidity and mortality

•  Clinically apparent disease

•  Mode of transmission

•  An effective vaccine

•  Social and economic factors

 

39.1 Classification

All human pox viruses are in the Chordopoxovirinae subfamily, and most of them belong to either the Orthopoxvirus (variola, vaccinia, cow pox) or the Parapoxvirus (Orf virus) genus.

Figure 39.1 Classification of poxviruses: