Resident in Internal Medicine, Mayo School of Graduate Medical Education, Rochester, MN (H.L.T.); Advisor to resident and Consultant in Infectious Diseases, Mayo Clinic, Rochester, MN (L.M.B.). A 26-year-old-man who had been living in Indonesia until 4 months previously presented to our hospital for evaluation of fever, agitation, and altered mental status. He had been seen previously at another facility for vague abdominal pain, nausea, and fever. He had become subacutely agitated and was transferred to our institution because of altered mental status and vomiting. On admission, he was febrile (temperature, 39.3 C) and tachycardic (heart rate, 118 beats/ min); his blood pressure was 134/96 mm Hg, and his oxygen saturation was 100% while breathing room air. Physical examination findings were notable for intermittent altered mental status with restlessness, agitation, inattention, and pain with neck flexion and posterior neck palpation. Findings on work-up at the outside facility included a sodium level of 118 mmol/L and no abnormalities detected on head computed tomography (CT) and chest radiography. His pupils were mildly constricted but responded to light. Admission laboratory studies yielded a normal white blood cell count of 10.1 10/L and an improved sodium concentration of 133 mmol/L.