A 19-year-old woman is evaluated in the emergency department for a 2-day history of fever, headaches, and jaundice. She vacationed in Hawaii 1 month ago and reports swimming in lakes and rivers. She was diagnosed with a flu-like illness 2 weeks ago that resolved spontaneously. She reports no history of a rash. She is sexually active with one partner. She takes no medications other than an oral contraceptive.
On physical examination, she is alert and oriented. Temperature is 38.9 °C (102 °F), blood pressure is 92/60 mm Hg, pulse rate is 124/min, and respiration rate is 24/min. Generalized lymphadenopathy, conjunctival suffusion, and scleral icterus are noted. She has photophobia, and passive neck flexion elicits resistance and discomfort. The remainder of the examination is unremarkable.