Camelpox and its risk to the human population

Camelpox is mainly of economic importance due to its relatively high mortality, loss of condition and fall in milk production and weight of affected camels. Clinically, two distinct types can be distinguished: the severe, generalized form, which appeared more frequently among young animals and the milder, localized form encountered more often in older camels. A higher incidence of illness and a twice higher case fatality rate were observed among male camels. Deaths occurred in 30% of the observed outbreaks with the highest case fatality in a single outbreak being 28%. Electron microscopy was found to be the most reliable test for detection of poxviruses in skin specimens taken from diseased animals. From the 465 camel herdsmen handling affected camels, the majority of whom were unvaccinated against smallpox, only a few developed skin eruptions. All skin specimens taken from them remained negative for poxviruses. From 335 specimens taken from skin lesions of persons who might come into direct or indirect contact with diseased animals, none was found to be positive for poxviruses. From an estimated 20 000 persons at risk, only one report of a possible case of human camelpox, which remained laboratory unconfirmed, was received. A few thousand camel herdsmen and their family members, interviewed in observed enzootic areas, strongly believed that camelpox is not transmissible to man. Although there have been reports in previous literature that man can be infected through handling affected camels, experience during the smallpox eradication campaign in Somalia in 1978-1979 suggests that human camelpox very rarely, if ever, occurs.