A 28-year-old man presents to the emergency department with a 5-day history of progressive malaise, anorexia, and nausea. For the past 2 days, he has also noted dark-colored urine and was told by his wife that his eyes appeared yellow. He works as a line cook and recently returned from a 10-day trip to Mexico 3 weeks ago, where he frequently consumed food and drinks from street vendors. His past medical history is unremarkable. He is not on any regular medications and denies use of supplements or over-the-counter drugs other than occasional acetaminophen for headaches, with his last dose over a month ago. He has no known allergies. He doesn’t recall if his childhood immunizations are up to date, and he did not attend any travel medicine consultation before traveling. He drinks alcohol socially (~2-3 drinks per week) and denies any intravenous or illicit drug use. He is in a monogamous relationship and denies any new sexual partners.

Initial laboratory studies are as follows:

WBC: 8,500/mm³ (4,500-11,000)

Segmented neutrophils: 55% (40-75)

Lymphocytes: 35% (20-45)

Hemoglobin: 14.8 g/dL (13.5-17.5)

Hematocrit: 44% (41-53)

Platelets: 280,000/mm³ (150,000-450,000)

PT: 12 seconds (11-13.5)

aPTT: 31 seconds (25-35)