II. Epidemiology
- Incidence: 200 to 300 cases per year
- Region: Most common in Rocky Mountains
III. Pathophysiology
- Cause: RNA orbivirus
- Transmission
- Dermacentor andersoni (wood Tick Bite)
- Infected Blood Transfusion
IV. Risk Factors for severe infection
- Asplenic patients
- Immunocompromised patients
V. Symptoms: Influenza-like illness
- Timing
- Onset 3-5 days after inoculation (Tick Bite)
- Symptom duration 7-10 days
- Pharyngitis
- Biphasic high fever (saddle-back fever)
- Meningitis
- Rash
- Conjunctivitis
- Photophobia
- Retro-orbital Headache
VI. Diagnosis
-
Serology
- Confirms diagnosis at 2-4 weeks
- PCR
- Reverse-transcriptase PCR can make the diagnosis within days of onset
VII. Differential Diagnosis
VIII. Labs
- Blood smear with immunofluorescent stain for virus
- Complete Blood Count
IX. Management
- Symptomatic (self-limited, no specific treatment exists)
X. Complications: Uncommon
- Encephalitis
- Myocarditis
- Pneumonitis
- Hepatitis
- Disseminated Intravascular Coagulation