Rift Valley Fever

Rift Valley fever is a viral hemorrhagic fever caused by a phlebovirus, endemic to parts of sub-Saharan Africa and the Arabian Peninsula, primarily affecting livestock (with associated significant agricultural and economic impact during outbreaks) but capable of causing human infection and, periodically, significant human outbreaks.

Transmission occurs through mosquito bites, or, more commonly in human cases during livestock outbreaks, through direct contact with the blood, body fluids, or tissues of infected animals, which is why abattoir workers, veterinarians, and herders are at particularly elevated risk during epizootic periods.

The large majority of human infections are asymptomatic or cause a mild, self limiting febrile illness, and it is this mild presentation that accounts for most cases, with severe disease occurring in only a small minority.

• The typical mild illness presents with fever, headache, myalgia, and malaise, generally resolving within a week without specific treatment.
• A small proportion of patients progress to more severe complications, which define the clinically important minority of cases: ocular disease, with retinal lesions that can cause permanent visual impairment, typically becoming apparent one to three weeks after the initial illness; hemorrhagic fever, with jaundice, bleeding manifestations, and hepatic involvement, carrying significant mortality; and encephalitis, presenting with confusion, seizures, or focal neurological deficit, typically occurring somewhat later in the illness course than the hemorrhagic complications.

• Diagnosis is confirmed through RT-PCR detection of viral RNA, most sensitive early in the illness during the viremic phase.
• Serology (IgM and IgG) supports diagnosis, particularly useful once the acute viremic window has passed, with IgM indicating recent infection.
• FBC and LFTs support assessment of severity, particularly relevant in suspected hemorrhagic presentations, where thrombocytopenia and deranged liver function may be present alongside coagulopathy.
• A relevant epidemiological context, livestock exposure, residence in or travel to an endemic or outbreak affected area, is an essential part of the diagnostic picture given the non-specific nature of the illness in isolation.

Differentials include other viral hemorrhagic fevers, malaria, and other causes of an acute febrile illness, with the specific epidemiological exposure context helping to narrow this differential considerably.

No specific antiviral treatment is established, and management is entirely supportive.

• Mild disease requires only symptomatic treatment: rest, hydration, and antipyretics or analgesics, avoiding NSAIDs and aspirin where a hemorrhagic complication cannot yet be excluded, given the bleeding risk these agents carry.
• Severe hemorrhagic disease requires the same principles of supportive care applied to other viral hemorrhagic fevers: careful fluid and electrolyte management, blood product support for significant bleeding or coagulopathy, and close monitoring for progression, generally in a higher level care setting.
• Ocular involvement requires ophthalmological assessment and follow up, given the risk of permanent visual impairment from retinal lesions.
• Encephalitis is managed supportively, following general principles applicable to viral encephalitis of other causes.
• Prevention centers on vector control, personal protective measures against mosquito bites in endemic and outbreak affected areas, and, critically, appropriate protective equipment and precautions for those handling livestock or animal tissues during outbreak periods, alongside livestock vaccination programs (used in animals rather than routinely in humans, given that human vaccines remain primarily investigational or reserved for specific high risk occupational groups in some settings) as part of broader One Health outbreak control efforts.

Referral: infectious disease or tropical medicine input for confirmed or suspected cases, particularly severe presentations; ophthalmology for any suspected ocular involvement; public health notification given the outbreak potential and the need for coordinated human and veterinary public health response.