Harrison's PodClass: Internal Medicine Cases and Board Prep Ep 183: A 75-Year-Old with Acute Fever and Altered Mental Status
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Feb 19, 2026 A 75-year-old with fever and acute confusion after mosquito exposure sparks a deep dive into encephalitis signs and diagnostic reasoning. The discussion highlights why West Nile virus is high on the differential and how CSF testing guides diagnosis. Imaging limits and the role of empiric antiviral therapy are reviewed. Recovery timelines and possible long-term neurologic effects are also covered.
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Travel And Mosquito Exposure Trigger Concern
- A 75-year-old man developed two days of fever, lethargy, agitation, disorientation, and visual hallucinations after a Montana trip.
- His family reported mosquito exposure and concurrent mild viral illness in other members, suggesting a vector-borne cause.
Encephalitis Is Clinically Diverse
- Encephalitis is brain inflammation from infection or autoimmune causes and often presents with fever and altered consciousness.
- Symptoms vary widely, including hallucinations, seizures, focal deficits, and behavioral changes that reflect affected brain regions.
West Nile Leads U.S. Arboviral Encephalitis
- Herpes simplex, varicella zoster, and Epstein-Barr are common sporadic viral causes, while arboviruses cause epidemics.
- West Nile virus is now the most common arboviral cause of encephalitis in the U.S.
