Rift Valley fever

Rift_Valley_fever_health_topic_imageWhile most human cases are relatively mild, a small percentage of patients develop a much more severe form of the disease. This usually appears as one or more of three distinct syndromes: ocular (eye) disease (0.5-2% of patients), meningoencephalitis (less than 1%) or haemorrhagic fever (less than 1%).The Rift Valley fever virus of the genus Phlebovirus and family Bunyaviridae is a cause of zoonotic viral disease that primarily causes abortion and death among domestic ruminants. Infection in humans is acquired through mosquito (mainly Aedes is the responsible vector for animal and also human transmission with other mosquitos (like Anopheles and Culex and also other haematophagous flies) bites or through contact with tissues of infected animals, and it is usually associated with uncomplicated acute febrile illness.

To date, no human-to-human transmission has been reported. The incubation period of the diseases is between 3 and 6 days. Symptoms of uncomplicated infections may include fever, headache, generalized weakness, dizziness, weight loss, myalgia and back pain. Some patients also have stiffness of the neck, photophobia and vomiting. Most people recover spontaneously within two days to a week. However, severe complications, such as haemorrhagic disease, meningo-encephalitis, and retinitis, occur in less than 3% of the cases.

Since 1931, when the first isolation of the virus occurred and the first detailed description of the disease in animals in the Rift Valley of Kenya was reported, many countries in eastern and southern Africa reported the disease and it is almost endemic in sub-Saharan Africa. Epidemics occur in this region when heavy rainfalls cause infected mosquito eggs to hatch, and large numbers of susceptible animals are present. Rift Valley fever first appeared outside Africa in 2000, when outbreaks were reported in Saudi Arabia and Yemen. Saudi Arabia and Yemen, in addition to Somalia, Sudan and Egypt are the countries of the Region reporting human cases of the virus.

Vector control activities, including awareness-raising ramong high-risk groups, conducting mass vaccination of animals during epidemics, and implementing infection prevention and control measures for those who are dealing with animal or human patients are playing a major role in reducing the burden of the disease in endemic countries. A human vaccine has been developed but its availability is limited.

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