Rift Valley Fever

Distribution
Sub-Saharan Africa and Egypt.

Infecting agent
A phlebovirus.

Vector
Mosquitoes. It also affects sheep, cattle and various other wild and domestic animals. Spread can be via the aerosol route from infected animal tissues and blood to blood contact as with other Viral Heaemorrhagic Fevers. Blood from viraemic humans is highly infectious but person to person spread in conditions of good hygiene is very unusual.

Incubation
3-7 days.

The illness
fever, headache, arthralgia and myalgia, and photophobia.
Compete recovery is usual although a few (<5%) cases develop haemorrhagic complications, liver failure (can mimic yellow fever) and neurological complications including retinal vasculitis. Diagnosis is made serologically in specially dedicated laboratories.

Treatment
Rift Valley fever cases should be managed in isolation as for other VHFs. Symptomatic care is indicated. In severe illnesses, ribavirin may be helpful as may convalescent serum from recovered patients.

Prevention is through avoiding mosquito bites. An expensive vaccine is available for laboratory workers at risk and vaccines have been used with some success in animals.

Recommended for more information
'Lecture Notes in Tropical medicine' Dion R. Bell. Blackwell Publications ISBN 0-632-02445-0
Mansons textbook of Tropical Diseases' Ed: G.C.Cook. WB Saunders Company Ltd ISBN 0-7020-1764-7.