General Description

Virus Classification

The smallpox virus, or variola virus, is part of the Poxviridae family, genus Orthopox. (19:4) Of the many orthopoxviruses in existence, there are only four that are known to infect humans; variola (smallpox), monkeypox, vaccinia and cowpox. Variola and monkeypox typically cause systemic infections, whereas vaccinia and cowpox typically cause localized infections in human hosts with normal immune responses. (22:V5:6) (19:4) Humans are the only natural host for smallpox. (15:141)

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