Fever in the Ozarks

A 58-year-old man from rural Missouri presents to an urgent care clinic with four days of abrupt high-grade fever, shaking chills, a severe bifrontal headache, diffuse myalgias, nausea, and anorexia. He returned from a three-day deer hunting trip in the Ozarks ten days ago and recalls pulling two small ticks from his lower extremities on the last day of the trip. He has no significant medical history, takes no medications, and denies any rash, neck stiffness, joint pain, cough, or dyspnea.

On examination, temperature is 39.8°C, heart rate 108/min, blood pressure 108/70 mmHg, respiratory rate 18/min, and oxygen saturation 97% on room air. He appears acutely ill and fatigued. No rash is identified on full skin survey including the palms and soles. The liver edge is palpable 2 cm below the right costal margin. No lymphadenopathy and no splenomegaly are detected.

Laboratory studies show white blood cells 2.4 x 10^3/uL with 62% neutrophils, 22% lymphocytes, and 10% monocytes, hemoglobin 13.8 g/dL, and platelets 68 x 10^3/uL. AST is 182 U/L, ALT is 148 U/L, LDH is 512 U/L, creatinine is 1.5 mg/dL, and sodium is 126 mEq/L. A peripheral blood smear is examined (see image). Blood cultures are obtained and pending. A chest radiograph is unremarkable.