Tanapox (a virus from the genus Yatapoxvirus) was first seen among individuals in the flood plain of the Tana River in Kenya during two epidemics (1957 and 1962) of acute febrile illness accompanied by localized skin lesions.
[1] The incubation period in human cases remains unknown, but in a person who underwent voluntary inoculation, erythema and central thickening appear by the fourth day.
[1] Most patients present a mild pre-eruptive fever that lasts 3–4 days, severe headaches and backaches, and often itching at the site where the skin lesion develops.
[citation needed] Tanapox virus in humans produces increased thickening of the epidermis with extensive degeneration of the prickle cell layer.
It is hypothesized that tanapox virus may be transferred from monkeys or another reservoir host to humans by infected arthropods that act as mechanical vectors.