Ref: CHB/Flash/2007/34                                             Date: February 27, 2007

CHB NEWS FLASH

What is Rift Valley Fever (RVF)?

Rift Valley Fever (RVF), is a zoonosis (a disease which primarily affects animals, but occasionally causes disease in humans). It may cause severe disease in both animals and humans leading to high morbidity and mortality. The death of RVF-infected livestock often leads to substantial economic losses. It is most common during years of heavy rainfall.

53 people died in Kenya in the last week after the outbreak of Rift Valley Fever, bringing the death toll to 148, as reported on Thursday by the Kenyan authorities. RVF is feared to have spread to Tanzania, after two people died from the virus in the northern region of Arusha. One person is believed to have died after contracting RVF at Gibasso Village in Tarime District, Mara Region recently.

Many different species of mosquitoes are vectors for the RVF virus. There is, therefore, a potential for epizootics (epidemics amongst animals) and associated human epidemics following the introduction of the virus into a new area where these vectors are present. This has been demonstrated in the past and remains a concern.

What causes Rift Valley Fever?

This is caused by a virus which was first isolated in 1930 in the Rift Valley of Kenya.

Where is Rift Valley fever found?

RVF is most common in the livestock-raising regions of eastern and southern Africa. The disease is also found in most countries of sub-Saharan Africa and in Madagascar.

How do people get Rift Valley fever?

1.     People can get RVF from the bite of mosquitoes and possibly other blood-sucking insects. The virus usually lies dormant in the eggs of Aedes mosquitoes. During heavy rains and floods, the eggs hatch large numbers of infected mosquitoes that feed on livestock and spread the virus. Other species of mosquitoes, and possibly other biting insects, can also become infected and spread the disease. The occurrence of disease in a large number of domestic animals is referred to as an "epizootic". The presence of a mosquito-borne epizootic can lead to an epidemic in humans.

2.     People can get RVF if they are exposed to the blood or other body fluids of infected animals. This can happen during the slaughtering or handling of infected animals or during the preparation of food.

3.     Laboratory workers have become infected through airborne transmission during work with virus cultures or laboratory samples containing the virus.

How is it transmitted from animals to humans?

      RVF virus is primarily spread amongst animals by the bite of infected mosquitoes. Many types of animals may be infected with RVF, including cattle, sheep, camels and goats.

      Direct contact with infected animals or infected products e.g. blood, milk, meat, etc.

      Through the bites of mosquitoes which may have fed on infected animals. (Many different species of mosquitoes e.g. Aedes, Culex, even Anopheles are vectors for the RVF virus.

What is the infectious agent that causes Rift Valley fever?

The disease is caused by the RVF virus.

Do people get sick immediately they are bitten by the mosquitoes?

No, it may take 2-6 days before they start showing signs/symptoms of the disease.

What are the signs and symptoms of the disease?

People with Rift Valley virus infections typically have a flu-like illness with fever, weakness, back pain, dizziness, and weight loss. Infected people usually get better in 2 days to 1 week after the start of the illness. Sometimes, however, the infection can cause hemorrhage (severe bleeding), encephalitis (inflammation of the brain), or severe eye complications.  

How is Rift Valley fever diagnosed?

Diagnosis can be made by use of several types of laboratory tests.

Who is at risk for Rift Valley fever?

1.     People who sleep outdoors at night in areas where outbreaks occur

2.     Animal herdsmen, slaughterhouse workers, veterinarians, and others who handle tissues of infected animals in areas where the virus is present

3.     International travelers who visit areas where the virus is present during periods when outbreaks or epidemics are occurring

What is the treatment for Rift Valley fever?

The drug ribavirin is being studied for its effectiveness against RVF.

What complications can result from Rift Valley fever?

     The most common complication is inflammation of the retina (a structure connecting the nerves of the eye to the brain). About 1% to 10% of affected persons might have some resulting vision problems or partial blindness.

      Approximately 1% of infected people die of the disease. Those who die are usually malnourished, sick with other diseases, or far from good medical care. Death rates are much higher for infected animals.

How can Rift Valley fever be prevented?

No licensed vaccine or virus-killing medicine is available for human use. Travelers to Africa should always wear long sleeves and pants and use insect repellents and bednets to protect against bites from mosquitoes and other blood-sucking insects. Persons who work with animals in areas where the virus is present should avoid exposure to the blood or tissues of potentially infected animals.

What is the infectious agent that causes Rift Valley fever?

The disease is caused by the RVF virus.

Prevention:

To prevent RVF, travelers to Africa should take precautions against insect bites: 1) use insect repellent, 2) wear long sleeves and pants, and 3) use bednets. Travelers should also avoid contact with livestock in areas where outbreaks of Rift Valley fever (RVF) are occurring.

This News Flash is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have any questions about the disease described above, consult a health-care provider.

“Community’s health – CHB’s priority”