Rift Valley fever is an acute febrile illness caused by the Rift Valley fever virus, which belongs to the Bunyaviridae family, Phlebovirus genus.
Here are some key points to know about Rift Valley Fever.
- The Rift Valley fever virus was first isolated in the course of an investigation into an epidemic among sheep on a farm in the Rift Valley of Kenya in 1931.
- It is a viral zoonosis that mainly affects animals (usually cattle and sheep). But, humans too can acquire the infection.
- Transmission of infection to humans is mainly via contact with blood or organs of infected animals through the handling of animal tissue during slaughtering or butchering, assisting with animal births, conducting veterinary procedures, or from the disposal of carcasses or fetuses.
- Herders, farmers, slaughterhouse workers, and veterinarians are at greater risk of acquiring the infection.
- Transmission to humans may also occur via bites from infected mosquitoes mainly Aedes and Culex.
- To date, no case of human-to-human transmission of RVF virus has been documented.
- Outbreaks of Rift Valley fever have been reported from sub-Saharan Africa, North Africa, following heavy rainfall, which increases the number of mosquitoes. However, in 2000, outbreaks were reported for the first time outside Africa in Saudi Arabia and Yemen. Therefore, the virus may well spread to other countries in Asia and Europe.
- The incubation period is 2-6 days.
- Most infected persons are either asymptomatic or have mild symptoms. The most frequently reported symptoms include fever, headache, bleeding, malaise, muscle pain, back pain, vomiting, and joint pain.
- Severe disease presents as either ocular disease, meningoencephalitis or hemorrhagic fever.
- The overall total case fatality rate is less than 1%. Case fatality is highest in patients with hemorrhagic fever (around 50%), which first manifests as jaundice and then with signs of hemorrhage – hematemesis, melena, purpuric rash or ecchymoses, epistaxis, menorrhagia, bleeding from gums or venepuncture sites.
- Diagnosis: Detection of viral RNA by polymerase chain reaction (RT-PCR) or detection of IgM antibodies against RVF virus by enzyme-linked immunosorbent assay (ELISA) or virus isolation by cell culture. All specimens must be handled with extreme care. Standard precautions must be strictly adhered to.
- Treatment: No specific treatment in mild infection; in severe cases, general supportive therapy is the main line of management.
- An inactivated vaccine has been developed for human use. But it is not licensed and is not commercially available. It has been used experimentally to protect veterinary and lab personnel at high risk of exposure to RVF.
- Prevention: The public must be educated about the risk factors for spread of the virus, especially in endemic areas. Gloves and other personal protective equipment must be used when handling sick animals or their tissues or slaughtering to avoid exposure to potentially infected blood or tissue. Mosquito repellents and nets should be used to protect from mosquito bites. All healthcare workers should follow standard precautions when handling specimens from patients.
(Source: Uptodate, WHO, CDC)