Fever From the Forest

A 32-year-old previously healthy man presents to a travel medicine clinic with 9 days of fever, severe headache, diffuse myalgias, and fatigue. He returned 2 weeks ago from a 12-day trekking expedition through the Annapurna region of rural Nepal, where he hiked through forested trails, tall grass, and scrubby riverside vegetation. He recalls multiple insect bites during the trip but did not notice anything unusual at the time. He took no pre-travel prophylaxis. He has no prior medical history and takes no medications.

On examination he is febrile to 39.6°C, blood pressure 106/68 mmHg, heart rate 104 bpm, and oxygen saturation 97% on room air. He appears systemically unwell. There is a non-pruritic maculopapular rash over the trunk and proximal extremities. Mild hepatosplenomegaly is present. Cervical and axillary lymphadenopathy is palpable bilaterally. On careful inspection of the skin, including intertriginous areas, a single painless lesion is found in the right axilla: a 12 mm punched-out ulcer with a central black crust, surrounded by a rim of erythema, on otherwise non-inflamed skin.

White blood cell count is 4,200/μL with a left shift. Platelet count is 74,000/μL. AST is 112 U/L and ALT is 98 U/L. Serum creatinine, electrolytes, and bilirubin are normal. CRP is 186 mg/L.