Rift Valley fever (RVF) is an acute, fever-causing viral disease that affects domestic animals (such as cattle, buffalo, sheep, goats, and camels) and humans.

Rift Valley Fever is generally found in regions of eastern and southern Africa where sheep and cattle are raised. However, Rift Valley Fever virus also exists in most countries of sub-Saharan Africa and Madagascar. Cases have also been confirmed in Saudi Arabia and Yemen in the Arabian Peninsula.

How is RVF virus spread among animals?

An outbreak of Rift Valley Fever among animals is generally observed during years in which heavy rainfall and localized flooding occur. The excessive rainfall allows mosquito eggs, usually of the genus Aedes, to hatch. The mosquito eggs are naturally infected with the Rift Valley Fever virus, and the resulting mosquitoes transfer the virus to the livestock on which they feed. Once the livestock is infected, other species of mosquitoes can become infected from the animals and can spread the disease. In addition, it is possible that the virus can be transmitted by other biting insects.

The virus was first identified in 1931 during an investigation into an epidemic among sheep on a farm in the Rift Valley of Kenya.

How do humans get RVF?

Humans can get RVF as a result of bites from mosquitoes and possibly other blood-sucking insects that serve as vectors. Humans can also get the disease if they are exposed to either the blood or other body fluids of infected animals. This exposure can happen during the slaughtering or handling of infected animals or by touching contaminated meat during the preparation of food. Infection through aerosol transmission of RVF virus has resulted from contact with laboratory specimens containing the virus.

What are the symptoms of RVF?

Persons with RVF may not have any symptoms but others may experience mild to severe disease. They usually experience an influenza-like illness, with sudden onset of fever, headache, muscle pain and backache. Some patients might have neck stiffness, discomfort when looking at bright lights, drowsiness and vomiting. Patients usually recover within two days to one week after onset of the illness. However, in some patients the illness can progress to haemorrhagic fever, encephalitis (infection of the brain) or infection of the eye.

Are there complications after recovery?

The most common complication associated with RVF is inflammation of the retina (a structure connecting the nerves of the eye to the brain). As a result, approximately 1% – 10% of affected patients may have some permanent vision loss.

Is the disease ever fatal?

Approximately 1% of humans that become infected with RVF die of the disease.

How is RVF treated?

There is no specific treatment for patients infected with RVF virus. Most human cases of RVF are relatively mild and of short duration. For the more severe cases, the mainstay of treatment is general supportive therapy.

Who is at risk for the illness?

Studies have shown that sleeping outdoors at night in regions where outbreaks occur could be a risk factor for exposure to mosquito and other insect vectors. Animal herdsmen, abattoir workers, and other individuals who work with animals in RVF-endemic areas (areas where the virus is present) have an increased risk for infection. Persons in high-risk professions, such as veterinarians and slaughterhouse workers, have an increased chance of contracting the virus from an infected animal. International travelers increase their chances of getting the disease when they visit RVF-endemic locations during periods when sporadic cases or epidemics are occurring.

How is RVF prevented?

A person’s chances of becoming infected can be reduced by taking measures to decrease contact with mosquitoes and other blood-sucking insects through the use of mosquito repellents and mosquito bed nets. Avoiding exposure to blood or tissues of animals that may potentially be infected is an important protective measure for persons working with animals in RVF-endemic areas