Crimean-Congo haemorrhagic fever (CCHF), Ebola, Lassa fever, Marburg fever and rift valley fever (RVF) are the most important zoonotic viral haemorrhagic fevers for humans.
Crimean-Congo haemorrhagic fever (CCHF) occurs in isolated cases and in limited outbreaks. The main natural hosts are hares, hedgehogs, cattle, sheep, goats, horses and swine.
The human disease occurs in rural areas in Africa, Asia and Europe. Humans acquire the infection from the bite of an infected tick and exposure to infected materials (family members of a patient, hospital personnel and agricultural workers for example).
Marburg viral haemorrhagic fever and Ebola viral haemorrhagic fever are diseases with a high case fatality ratio. Reservoirs in nature are unknown.
Lassa fever is a haemorrhagic fever endemic in four African countries: Guinea, Liberia, Nigeria and Sierra Leone. The reservoir is a rodent species (Mastomys sp.).
Rift Valley Fever is endemic in Africa and recently emerged in the Middle East. It occurs naturally in sheep, goats, cattle, camels and buffaloes. Mosquitoes are the principal mode of virus transmission between animals. Man is infected during contact with infected animals.