Rift valley fever is a viral infection carried by mosquitoes that is endemic to sub-Saharan Africa. Initial symptoms are a flu-like illness with arthralgias, lower backache, photophobia, and headache. Two severe complications that occur in about 1% of cases are encephalitis and hemorrhagic fever.
CASES/YEAR
0 (US); 5,000 (Global)
INCUBATION
2-7 days; [CCDM]
INITIAL SYMPTOMS
Severe flu-like illness lasting for about 4 days; About 1% of patients develop complications (ocular, meningoencephalitis, or hemorrhagic liver failure. [CCDM, p. 521]
PRECAUTIONS
No person-to-person transmission; [ABX Guide]
COMMENTS
FINDINGS
Initial symptoms are a flu-like illness with arthralgias, lower backache, photophobia, and headache. Two severe complications that occur in about 1% of cases are encephalitis and hemorrhagic fever. Hemiparesis and coma occur in encephalitis. The hemorrhagic fever is associated with hepatitis, jaundice, hemorrhages, and renal failure. Another complication is retinitis. [Guerrant, p. 464] Complications of this mosquito-borne viral infection include encephalitis, hepatitis, and hemorrhages. Fever may be biphasic. [CCDM, p. 521] Retinal vasculitis occurs in about 10% of patients with otherwise mild infections and can result in visual impairment. [Harrisons, p. 570]
EPIDEMIOLOGY:
Sheep and other domestic ruminants (sheep, goat, cattle, camels) are reservoirs. Workers may be infected handling tissues of animals (necropsy or butchering), and aerosols have transmitted infection in the laboratory. The case-fatality rate is 1-5% but can be as high as 50% in hospitalized patients. [CCDM, p. 521-2] It is possible that transmission occurs by ingestion of raw milk. [www.who.int/mediacentre/factsheets] Domestic ungulates such as sheep and cattle serve as amplifiers during epidemics. [PPID, 8th Ed, p. 2026] Travelers to endemic areas should avoid mosquito bites and contact with livestock. An investigational vaccine has not been approved by the FDA. [CDC Travel, p. 375-6] Hemorrhagic fever occurs in less than 1% of patients and typically about 1-2 weeks after a wave of spontaneous abortions in livestock. [Cecil, p. 2225] Vaccination of livestock can prevent epidemics. A new vaccine for humans is being tested [Harrison ID, p. 969]
DIAGNOSTIC
PCR; Serology; Culture; Antigen detection by ELISA; [CCDM] Detect virus during viremia with RT-PCR; Paired sera; [Cecil, p. 2226]
SCOPE
The virus is endemic to sub-Saharan Africa with epidemics reported in Egypt, Madagascar, Mali, Mauritania, Senegal, Sudan & S. Sudan, Uganda, Kenya, Somalia, Tanzania, Saudi Arabia, Yemen, South Africa, Botswana, and Namibia; [CDC Travel, p. 374]
SIGNS & SYMPTOMS
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>arthralgia
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>fever
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>fever, biphasic or relapsing
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>myalgia
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E epistaxis
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G abdominal pain
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G jaundice
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G liver function test, abnormal
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G nausea, vomiting
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H anemia
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H thrombocytopenia
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N confusion, delirium
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N headache
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N lethargy
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N stiff neck
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O conjunctivitis, acute
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S petechiae and ecchymoses
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*acute renal failure
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*bleeding tendency
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*blindness
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*encephalitis
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*hepatitis
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*meningitis
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*paralysis
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*shock
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*stupor, coma
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*uveitis
ENTRY
Inhalation, Ingestion, Skin or Mucous Membranes (Includes Conjunctiva)
SOURCE
Animal Tissue, Eating Contaminated Food, Eating Unpasteurized Milk or Cheese
RESERVOIR
Cattle, Goats and Sheep
RISK FACTORS
- Consume unpasteurized milk/cheese
- Handle animal carcasses or placentas
- Travel to endemic area
- Victim--air release of infectious agents
- Work in a medical or research lab
TREATMENT
No specific treatment; [CCDM, p. 523]
REFERENCES FOR CASES/YEAR
1.
2. (Global) Major outbreak in 1997-98 in Kenya, Somalia, & Tanzania; [Fact sheets from WHO 2013] The risk for travelers is considered low; [Public Health England website] RVF was confirmed in Saudi Arabia and Yemen in 2000. 200,000 infections (600 deaths) occurred in 1977-1978 in an outbreak in Egypt related to camels moving from Sudan; [Cecil, p. 2225] The last major epizootic occurred in Kenya in 1950-51 when about 100,000 sheep died. [CDC website] 100 to 100,000 cases/year; [Cecil, p. 2215] Guesstimate: 5000 cases/year;