Rift Valley fever is a mosquito-borne viral zoonosis caused by the RVF virus (genus Phlebovirus, family Phenuiviridae, order Bunyavirales), endemic throughout sub-Saharan Africa and the Arabian Peninsula. [1] Most human infections are subclinical or self-limiting febrile illness, but 1–2% progress to severe complications including hemorrhagic fever, encephalitis, retinitis, hepatorenal failure, and death. [2-3] The overall case fatality rate among hospitalized patients ranges from ~21–42% depending on the outbreak. [4-6] No licensed human vaccines or specific antivirals are currently available. [1-2]
1. History
- Exposure history is critical: Ask about travel to or residence in endemic areas (sub-Saharan Africa, Arabian Peninsula, Indian Ocean islands) [1][7]
- Direct contact with livestock — butchering, slaughtering, handling aborted material, milking, or consuming raw milk/meat from sick animals [5][7-8]
- Mosquito bite exposure (Aedes and Culex species), especially during/after heavy rainfall and flooding [2][9]
- Incubation period: 2–6 days (range 2–21 days for hemorrhagic fever viruses broadly) [10-11]
- Onset: Abrupt, with high fever, headache, myalgias, arthralgias (especially large joints), photophobia, and weakness [12-13]
- Symptom progression: Initial febrile illness → GI complaints (nausea, vomiting, abdominal pain) → jaundice, RUQ pain, delirium → hemorrhagic manifestations (in severe cases) [12]
- Timing of complications: Retinitis onset 4–15 days (mean ~8.8 days) after acute illness; encephalitis typically 2–3 weeks after acute illness [14-15]
- Pregnancy status — RVF is associated with spontaneous abortion (54% of pregnant cases) [4]
2. Alarm Features
- Hemorrhagic manifestations: Petechiae, mucosal bleeding, hematemesis, melena, epistaxis, hemoptysis [4][8][10]
- Jaundice with RUQ pain — suggests hepatocellular failure (present in up to 75% of severe cases) [6]
- Delirium, altered mental status, seizures — suggests encephalitis [12][16]
- Visual changes (blurred vision, scotomata) — suggests retinitis with risk of permanent blindness [14]
- Oliguria/anuria — acute renal failure (41% of hospitalized cases) [4][6]
- Shock, severe anemia, DIC — major predictors of mortality [6]
- Combination of hepatorenal failure + hemorrhage carries the highest mortality [6]
3. Medications
- No licensed antivirals for RVF in humans [1][17]
- Ribavirin: Has been used empirically in some VHF outbreaks; however, evidence for RVF is limited, and animal data suggest it may prevent acute hepatic disease but increase risk of delayed-onset neurologic disease. Contraindicated in pregnancy (teratogenic) [17-18]
- Favipiravir (T-705): Preclinical data show efficacy against RVFV in animal models, including reduced viral replication and protection against both acute and neuroinvasive disease. Not yet approved for human use in RVF [18-19]
- Avoid NSAIDs and anticoagulants in suspected hemorrhagic disease due to bleeding risk
- Avoid aspirin — risk of worsening hemorrhagic diathesis
- Empiric antibiotics may be considered if bacterial co-infection is suspected, but routine prophylaxis is not indicated [17]
4. Diet
- Avoid consumption of raw milk, blood, or undercooked meat from potentially infected animals — this is a major transmission route [7-8][20]
- Adequate hydration is essential, especially with GI losses (vomiting, diarrhea)
- NPO if severe hepatic failure or hemorrhagic manifestations with hemodynamic instability
- No specific long-term dietary restrictions post-recovery
5. Review of Systems
- Constitutional: Fever, malaise, fatigue, weakness, weight loss
- HEENT: Photophobia, blurred vision, scotomata, eye pain (retinitis/uveitis); conjunctival injection [10][14]
- GI: Nausea, vomiting, abdominal pain (especially RUQ), diarrhea, hematemesis, melena [4][12]
- Neurologic: Headache, confusion, delirium, seizures, neck stiffness (meningoencephalitis) [8][12]
- Hematologic: Easy bruising, petechiae, mucosal bleeding, epistaxis, hemoptysis [5][21]
- Musculoskeletal: Large-joint arthralgias, myalgias [12-13]
- Obstetric: Vaginal bleeding, signs of threatened abortion in pregnant patients [2][4]
- Renal: Decreased urine output, dark urine
6. Collateral History and Family History
- Occupational exposure: Butchers, herders, veterinarians, slaughterhouse workers, farmers — all at significantly increased risk [5][7][20]
- Contact with sick or recently aborted animals in the household or community
- Community reports of livestock abortions or neonatal animal deaths (sentinel event for outbreaks) [22]
- Co-travelers or household members with similar symptoms
- HIV status: Co-infection with HIV was associated with 75% mortality in one Tanzanian cohort [23]
- No known hereditary susceptibility; family history is relevant primarily for shared environmental/occupational exposures
7. Risk Factors
- Male sex (OR significantly elevated) [5][7][24]
- Age >20 years, with highest mortality in those >44 years [21][24]
- Occupational contact with livestock: Butchering, milking, handling aborted material, slaughtering [5][7]
- Consumption of raw animal products (milk, blood, meat) from infected animals [8][20]
- Mosquito exposure in endemic areas, especially during/after heavy rains and flooding [9][25]
- Residence in the "cattle corridor" regions of East Africa [5][26]
- Immunocompromised status (e.g., HIV) [23]
- Pregnancy — increased risk of severe disease and fetal loss [2][4]
- Climate factors: Heavy rainfall, flooding, proximity to water bodies [9][26]
8. Differential Diagnosis
The nonspecific early presentation makes differentiation challenging: [4][10]
- Malaria — Most important mimic in endemic areas; co-infection is common (55% in one Tanzanian outbreak). Thick/thin smear and rapid diagnostic test essential [23]
- Dengue fever — Fever, thrombocytopenia, hemorrhagic manifestations; distinguished by NS1 antigen/serology
- Yellow fever — Hepatitis, jaundice, hemorrhage; overlapping geography in Africa
- Ebola/Marburg virus disease — Hemorrhagic fever with higher CFR; contact tracing critical
- Crimean-Congo hemorrhagic fever — Tick-borne VHF with hemorrhagic manifestations
- Leptospirosis — Hepatorenal syndrome, jaundice, conjunctival suffusion [27]
- Typhoid/enteric fever — Prolonged fever, abdominal pain, hepatosplenomegaly
- Viral hepatitis (A, B, E) — Jaundice, transaminitis; serology distinguishes
- Meningococcemia — If meningeal signs and petechiae predominate
- Hantavirus — Renal syndrome variant with hemorrhagic features
Key distinguishing features of severe RVF: Fever + large-joint arthralgia + GI complaints → jaundice + RUQ pain + delirium ± hemorrhage, in the context of livestock contact or mosquito exposure in an endemic area. [12]
9. Past Medical History
- Prior RVF infection confers long-lasting immunity [3]
- HIV/AIDS — dramatically increases mortality risk [23]
- Chronic liver disease — may worsen hepatic manifestations
- Chronic kidney disease — increased vulnerability to renal failure
- Pregnancy — high risk for spontaneous abortion and severe disease [2][4]
- Prior VHF exposure or vaccination history (no licensed human vaccine, but investigational vaccines exist) [2-3]
10. Physical Exam
- Vitals: High fever, hypotension, relative bradycardia, tachypnea [10]
- General: Acutely ill, toxic-appearing in severe cases
- Eyes: Conjunctival injection/hemorrhage; fundoscopy may reveal macular/paramacular retinal lesions, retinal hemorrhages, vitreous haze, optic disc edema [14][28]
- Skin: Petechiae, purpura, ecchymoses; cutaneous flushing possible [10]
- Abdomen: RUQ tenderness, hepatomegaly, jaundice [6][12]
- Neurologic: Altered mental status, delirium, meningismus, focal deficits (in encephalitic form) [8][12]
- Lymph nodes: Congestion and edema may be present [29]
- Pulmonary: Congestion, edema in severe/terminal cases [29]
11. Lab Studies
- CBC: Thrombocytopenia, leukopenia, anemia [8][30]
- CMP/LFTs: Markedly elevated AST/ALT (hepatocellular necrosis is the hallmark pathology), elevated bilirubin, elevated creatinine and BUN [6][8][27]
- Coagulation: PT/INR prolonged, fibrinogen low, D-dimer elevated (DIC) [10]
- Confirmatory testing:
- RT-PCR (acute phase, first 1–7 days of illness) — gold standard for early diagnosis [30-31]
- ELISA for IgM (appears during first week) and IgG (convalescent) [31-32]
- Virus isolation (requires BSL-3/4 facility) [13]
- Blood cultures to rule out bacterial sepsis and enteric fever [30]
- Malaria smear/RDT — essential to rule out co-infection in endemic areas [23][30]
- Type and screen — anticipate need for transfusion in hemorrhagic cases
12. Imaging
- Abdominal ultrasound: Hepatomegaly, hepatic necrosis pattern, ascites; useful to evaluate RUQ pain and hepatorenal status
- CT abdomen: If ultrasound inconclusive; may show hepatic changes, ascites
- CT/MRI brain: Indicated if encephalitis suspected (altered mental status, seizures, focal deficits) — may show cerebral edema, inflammatory changes [16]
- Chest X-ray: Pulmonary congestion/edema in severe cases; rule out secondary pneumonia
- Imaging is generally supportive rather than diagnostic; laboratory confirmation is essential [31]
13. Special Tests
- Fundoscopy/Ophthalmologic exam: Critical in all confirmed cases — macular/paramacular retinitis identified in all affected eyes in the Saudi outbreak; fluorescein angiography shows early hypofluorescence with late staining [14][28]
- Lumbar puncture: If meningoencephalitis suspected; CSF may show pleocytosis
- Immunohistochemistry on tissue samples (postmortem): Extensive hepatocellular necrosis without prominent inflammatory infiltrates is the most distinctive histopathologic finding [27]
- Seroneutralization assay: Reference standard for seroprevalence studies [32]
- No validated clinical scoring system specific to RVF; severity stratification is based on clinical syndrome (febrile vs. hemorrhagic vs. encephalitic vs. ocular) [4][11]
14. ECG
- No RVF-specific ECG findings are described in the literature
- ECG is indicated to evaluate for:
- Relative bradycardia (fever-pulse dissociation, as seen with other VHFs) [10]
- Electrolyte abnormalities secondary to renal failure (hyperkalemia → peaked T waves, widened QRS)
- Myocardial involvement if shock or multiorgan failure develops
- Monitor for arrhythmias in critically ill patients with DIC, shock, or severe electrolyte derangements
15. Assessment
Clinical spectrum ranges across nine recognized syndromes: [4]
- Self-limiting febrile illness (majority of cases) — fever, headache, myalgias, arthralgias lasting days to weeks [1][13]
- Hepatic syndrome — hepatocellular failure with jaundice (75% of severe cases) [6]
- Renal syndrome — acute renal failure (41%) [4][6]
- Hemorrhagic syndrome — bleeding manifestations (19–81% depending on cohort) [6][8]
- Neurologic syndrome — encephalitis (21%), typically delayed onset 2–3 weeks [4][15]
- Ocular syndrome — retinitis with 50% risk of permanent vision loss if macular lesions develop [14][33]
- Obstetric syndrome — spontaneous abortion (54%) [4]
Severity stratification: Hepatorenal failure, shock, and severe anemia are the major factors associated with death. [6] Hospital-based mortality in Uganda was 64% among those admitted. [21]
16. Treatment Plan
Initial Stabilization
- Aggressive supportive care is the mainstay — no approved disease-specific therapy exists [17]
- IV fluid resuscitation with crystalloids (normal saline or Ringer's lactate); titrate to clinical status [17]
- Correct coagulopathy: FFP, cryoprecipitate, platelets as indicated for DIC
- Blood transfusion for severe anemia/hemorrhage [6]
- Vasopressors for refractory shock
- Renal replacement therapy for acute renal failure if available
Symptom Management
- Antipyretics (acetaminophen preferred; avoid NSAIDs)
- Antiemetics for nausea/vomiting
- Seizure management with benzodiazepines → levetiracetam if encephalitic
Investigational Antivirals
- Ribavirin and favipiravir have shown preclinical efficacy but are not approved for RVF [18-19]
- No targeted therapeutic recommendations exist in current VHF guidelines for RVF specifically [17]
Ophthalmologic Management
- Urgent ophthalmology consultation for any visual complaints
- Anterior uveitis may respond to topical corticosteroids and cycloplegics [14]
Infection Control
- Standard and contact precautions; BSL-3/4 for laboratory handling [13]
- Notify public health authorities immediately — RVF is a notifiable disease and WHO priority pathogen [9][17]
17. Disposition
Admission Criteria
- Any hemorrhagic manifestations
- Jaundice or evidence of hepatic failure
- Acute renal failure
- Altered mental status, seizures, or meningeal signs
- Hemodynamic instability or shock
- Pregnancy with confirmed/suspected RVF
- Inability to tolerate oral intake
Observation/Short Stay
Discharge Criteria
- Resolution of fever for ≥48 hours
- Stable hemodynamics, no bleeding
- Adequate oral intake
- Improving labs (LFTs, renal function, platelets)
- Ophthalmologic evaluation completed or scheduled
Specialist Consultation Triggers
- Infectious disease: All confirmed/suspected cases
- Ophthalmology: Any visual complaints (urgent) [14]
- Nephrology: Acute renal failure requiring RRT
- Neurology/Neurosurgery: Encephalitis, seizures
- Critical care: Hemorrhagic shock, DIC, multiorgan failure
- OB/GYN: Pregnant patients
- Public health: Immediate notification for outbreak investigation [9]
18. Follow Up / Return Precautions
- Follow-up within 1 week of discharge for repeat labs (LFTs, renal function, CBC)
- Ophthalmologic follow-up at regular intervals — retinitis can present 1–3 weeks after acute illness; macular scarring, vascular occlusion, and optic atrophy are late sequelae [14][28]
- Neurologic monitoring for 4–6 weeks — encephalitis may develop 2–3 weeks post-acute illness [15-16]
- Symptom duration in survivors varies from 2 to 120 days; prolonged jaundice, visual difficulties, and GI symptoms are common [21]
Return precautions — instruct patients to return immediately for:
- New or worsening bleeding from any site
- Jaundice or dark urine
- Visual changes (blurred vision, floaters, vision loss)
- Confusion, severe headache, seizures, neck stiffness
- Decreased urine output
- Persistent vomiting or inability to keep fluids down
- Fever recurrence after initial improvement
Patient counseling
- Avoid contact with livestock and raw animal products until fully recovered
- Use mosquito repellent and bed nets to prevent re-exposure and onward transmission
- Natural infection confers long-lasting immunity [3]
- No licensed human vaccine is currently available, though several candidates are in clinical trials (ChAdOx1 RVF, hRVFV-4s) [2-3]
References
1. Rift Valley Fever: Biology and Epidemiology. — Wright D, Kortekaas J, Bowden TA, Warimwe GM. The Journal of General Virology. 2019.
2. Safety and Immunogenicity of the Live-Attenuated hRVFV-4s Vaccine Against Rift Valley Fever in Healthy Adults: A Dose-Escalation, Placebo-Controlled, First-in-Human, Phase 1 Randomised Clinical Trial. — Leroux-Roels I, Prajeeth CK, Aregay A, et al. The Lancet. Infectious Diseases. 2024.
3. Safety, Tolerability, and Immunogenicity of the ChAdOx1 RVF Vaccine Against Rift Valley Fever Among Healthy Adults in Uganda: A Single-Centre, Single-Blind, Randomised, Placebo-Controlled, Dose-Escalation, Phase 1 Trial. — Anywaine Z, Serwanga J, Ggayi AM, et al. The Lancet. Infectious Diseases. 2026.
4. Clinical Manifestations of Rift Valley Fever in Humans: Systematic Review and Meta-Analysis. — Anywaine Z, Lule SA, Hansen C, Warimwe G, Elliott A. PLoS Neglected Tropical Diseases. 2022.
5. Detection of Sporadic Outbreaks of Rift Valley Fever in Uganda Through the National Viral Hemorrhagic Fever Surveillance System, 2017-2020. — Nyakarahuka L, Whitmer S, Klena J, et al. The American Journal of Tropical Medicine and Hygiene. 2023.
6. Epidemic Rift Valley Fever in Saudi Arabia: A Clinical Study of Severe Illness in Humans. — Al-Hazmi M, Ayoola EA, Abdurahman M, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2003.
7. Paving the Way for Human Vaccination Against Rift Valley Fever Virus: A Systematic Literature Review of RVFV Epidemiology From 1999 to 2021. — Gerken KN, LaBeaud AD, Mandi H, et al. PLoS Neglected Tropical Diseases. 2022.
8. Severe Human Illness Caused by Rift Valley Fever Virus in Mauritania, 2015. — Boushab BM, Fall-Malick FZ, Ould Baba SE, et al. Open Forum Infectious Diseases. 2016.
9. The Increasing Threat of Rift Valley Fever Virus Globalization: Strategic Guidance for Protection and Preparation. — Gibson S, Noronha LE, Tubbs H, et al. Journal of Medical Entomology. 2023.
10. Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management. — Borio L, Inglesby T, Peters CJ, et al. The Journal of the American Medical Association. 2002.
11. The Challenging Management of Rift Valley Fever in Humans: Literature Review of the Clinical Disease and Algorithm Proposal. — Javelle E, Lesueur A, Pommier de Santi V, et al. Annals of Clinical Microbiology and Antimicrobials. 2020.
12. Severe Rift Valley Fever May Present With a Characteristic Clinical Syndrome. — Kahlon SS, Peters CJ, Leduc J, et al. The American Journal of Tropical Medicine and Hygiene. 2010.
13. Interplay Between the Virus and Host in Rift Valley Fever Pathogenesis. — Terasaki K, Makino S. Journal of Innate Immunity. 2015.
14. Ocular Complications of Rift Valley Fever Outbreak in Saudi Arabia. — Al-Hazmi A, Al-Rajhi AA, Abboud EB, et al. Ophthalmology. 2005.
15. CD4 T Cells, CD8 T Cells, and Monocytes Coordinate to Prevent Rift Valley Fever Virus Encephalitis. — Harmon JR, Spengler JR, Coleman-McCray JD, et al. Journal of Virology. 2018.
16. Rift Valley Fever Virus Activates Multiple Cell Death Pathways in Neurons. — Connors KA, Frey ZD, Demers MJ, et al. Journal of Virology. 2026.
17. Standard of Care for Viral Haemorrhagic Fevers (VHFs): A Systematic Review of Clinical Management Guidelines for High-Priority VHFs. — Rigby I, Michelen M, Dagens A, et al. The Lancet. Infectious Diseases. 2023.
18. Favipiravir (T-705) Protects Against Peracute Rift Valley Fever Virus Infection and Reduces Delayed-Onset Neurologic Disease Observed With Ribavirin Treatment. — Scharton D, Bailey KW, Vest Z, et al. Antiviral Research. 2014.
19. Preclinical Efficacy of a Favipiravir and Nitazoxanide Combination Against Rift Valley Fever Virus. — Chaput S, Driouich JS, Pastorino B, et al. Antiviral Research. 2026.
20. Drivers of Rift Valley Fever Epidemics in Madagascar. — Lancelot R, Béral M, Rakotoharinome VM, et al. Proceedings of the National Academy of Sciences of the United States of America. 2017.
21. Severe Morbidity and Hospital-Based Mortality From Rift Valley Fever Disease Between November 2017 and March 2020 Among Humans in Uganda. — Anywaine Z, Hansen C, Warimwe GM, et al. Virology Journal. 2024.
22. Epidemiological Investigation of a Rift Valley Fever Outbreak in Humans and Livestock in Kenya, 2018. — Hassan A, Muturi M, Mwatondo A, et al. The American Journal of Tropical Medicine and Hygiene. 2020.
23. Epidemiologic and Clinical Aspects of a Rift Valley Fever Outbreak in Humans in Tanzania, 2007. — Mohamed M, Mosha F, Mghamba J, et al. The American Journal of Tropical Medicine and Hygiene. 2010.
24. Understanding the Rift Valley Fever Exposure Risk: A Comparative Perspective From a Multi-Country Study in East and Central Africa, 2021-24. — Lepore L, Odinoh R, Dawa J, et al. PLoS Neglected Tropical Diseases. 2026.
25. Rift Valley Fever Epidemiology: Shifting the Paradigm and Rethinking Research Priorities. — Rostal MK, Thompson PN, Anyamba A, et al. The Lancet. Planetary Health. 2025.
26. Interepidemic Rift Valley Fever in East Africa: The Recent Risk Landscape and Projected Impacts of Global Change. — Eskew EA, Clancey E, Singh D, et al. Proceedings. Biological Sciences. 2026.
27. Pathologic Studies on Suspect Animal and Human Cases of Rift Valley Fever From an Outbreak in Eastern Africa, 2006-2007. — Shieh WJ, Paddock CD, Lederman E, et al. The American Journal of Tropical Medicine and Hygiene. 2010.
28. Rift Valley Fever Ocular Manifestations: Observations During the 1977 Epidemic in Egypt. — Siam AL, Meegan JM, Gharbawi KF. The British Journal of Ophthalmology. 1980.
29. Insights Into the Pathogenesis of Viral Haemorrhagic Fever Based on Virus Tropism and Tissue Lesions of Natural Rift Valley Fever. — Odendaal L, Davis AS, Venter EH. Viruses. 2021.
30. Post-Travel Evaluation of the Ill Traveler. — Ralph Huits, Davidson H. Hamer, and Michael Libman CDC Yellow Book. 2025.
31. Detection and Diagnosis of Rift Valley Fever Virus. — Bob NS, Dia M, Ndiaye O, et al. Methods in Molecular Biology. 2024.
32. External Quality Assessment of Rift Valley Fever Diagnosis in Countries at Risk of the Disease: African, Indian Ocean and Middle-East Regions. — Pedarrieu A, El Mellouli F, Khallouki H, et al. PloS One. 2021.
33. Rift Valley Fever Virus Infects the Posterior Segment of the Eye and Induces Inflammation in a Rat Model of Ocular Disease. — Schwarz MM, Connors KA, Davoli KA, et al. Journal of Virology. 2022.