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What is Rift Valley Fever?
Rift Valley Fever (RVF) is an insect-borne viral disease that primarily affects livestock and can cause an epidemic in animals (an "epizootic"). An RVF epizootic can lead to an epidemic among humans who are exposed to diseased animals.
Symptoms and outcome of RVF
RVF typically produces no symptoms or a mild illness associated with fever and liver abnormalities. However, in some cases the illness progresses to haemorrhagic fever (which can lead to shock or haemorrhage – internal bleeding), encephalitis (inflammation of the brain, which can lead to headaches, coma or seizures), or eye inflammation. One to ten percent of affected patients may have some permanent vision loss.
Patients who become ill usually experience fever, generalised weakness, back pain, dizziness and extreme weight loss at the onset of the illness. Recovery is usually within two days to one week after onset.
There is currently no established treatment for RVF.
Where does RVF occur?
RVF generally occurs in eastern and southern Africa where sheep and cattle are farmed. In 2000, a RVF outbreak was reported in Saudi Arabia and Yemen.
How does RVF spread?
An RVF epizootic generally occurs at times of very heavy rainfall, which allows mosquito eggs to hatch. The eggs are infected with RVF virus, and the resulting mosquitoes transmit the virus to livestock on which they feed. Other species of mosquitoes can then become infected from the livestock and spread the disease. It is also possible that other biting insects can transmit the virus.
Humans can get RVF from the bites of infected mosquitoes, and via exposure to blood or other body fluids of infected animals during slaughtering or handling infected animals or by touching contaminated meat during food preparation. Infection through aerosol transmission has resulted from laboratory specimens containing the virus.
Many different species of mosquitoes are vectors for the RVF virus. There is thus a potential for epizootics and associated human epidemics following the introduction of the virus into a new area where these vectors are present.
Who is at risk?
Sleeping outdoors at night in regions where outbreaks occur could be a risk factor for exposure to insect vectors. People such as herdsmen and abattoir workers who work with animals in endemic areas are at increased risk for infection.
International travellers increase their risk when visiting RVF-endemic locations at times when cases have been recently reported.
Can RVF be prevented?
You can reduce your infection risk by reducing exposure to bloodsucking insects e.g. through the use of mosquito repellents and nets. Avoiding exposure to fluids and tissues of potentially infected animals is important for persons working with animals in RVF-endemic areas.
Information sourced from the World Health Organisation and the Centres for Disease Control.
- (Health24, January 2007)
