1D44 Rift Valley fever

International Classification of Diseases for Mortality and Morbidity Statistics, 11th Revision, v2025-01

A disease caused by an infection with Rift Valley fever virus. This disease is commonly asymptomatic. This disease may also present with fever, liver abnormalities, weakness, back pain, or dizziness. Transmission is through the bite of an infected mosquito. Confirmation is commonly by detection of Rift Valley fever virus specific IgM or IgG antibodies in a blood sample. A disease caused by an infection with Rift Valley fever virus. The incubation period (the interval from infection to onset of symptoms) for RVF varies from 2 to 6 days. Most infections in human will lead to no symptoms or mild form of the disease characterized by a feverish syndrome with sudden onset of flu-like fever, muscle and joint pain and headache. Some patients develop neck stiffness, sensitivity to light, loss of appetite and vomiting; in these patients the disease, in its early stages, may be mistaken for meningitis. The symptoms of RVF usually last from 4 to 7 days, after which time the immune response becomes detectable with the appearance of antibodies and the virus disappears from the blood. A small percentage of patients develop a much more severe form of the disease. This usually appears as one or more of the three following syndromes: • Ocular (eye) form (0.5-2% of patients): symptoms associated with the mild form of the disease are accompanied by retinal lesions. The lesions in the eyes usually appear 1 to 3 weeks after the first symptoms. Patients report blurred or decreased vision. The disease may resolve itself within 10 to 12 weeks. However, when the lesions occur in the macula, 50% of patients will experience a permanent loss of vision. • Meningoencephalitis form (less than 1% of patients): The onset of the meningoencephalitis form usually occurs 1 to 4 weeks after the first symptoms of RVF appear. Clinical features include intense headache, loss of memory, hallucinations, confusion, disorientation, vertigo, convulsions, lethargy and coma. Neurological complications can appear two months or more later. While death rate in these patients is low, residual neurological deficit, which may be severe, is common. • Haemorrhagic fever form (less than 1% of patients): The symptoms of this form appear 2–4 days after the onset of illness, and begin with evidence of severe liver impairment. Subsequently signs of haemorrhage then appear such as vomiting blood, passing blood in the faeces, a purpuric rash or ecchymoses (, bleeding from the nose or gums, menorrhagia and bleeding from venepuncture sites. The case fatality ratio in these patients is high at approximately 50%. Death usually occurs 3 to 6 days after the onset of symptoms.. Rift Valley fever is a viral zoonosis that primarily affects animals but can also infect humans. Infection can cause severe disease in both animals and humans. Most human infections result from direct or indirect contact with the blood or organs of infected animals. The virus can be transmitted to humans 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. Certain occupational groups such as herders, farmers, slaughterhouse workers and veterinarians are therefore at higher risk of infection. Human infections have also resulted from the bites of infected mosquitoes, most commonly the Aedes and Culex mosquitoes. Confirmation that symptoms are caused by RVF virus infection are made using the following diagnostic methods. reverse transcriptase polymerase chain reaction (RT-PCR) assay or IgG and IgM antibody enzyme-linked immunosorbent assay (ELISA).

postcoordination

synonyms

• Rift Valley fever
• RFV – [Rift Valley fever]
• Encephalitis due to Rift valley virus

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