An acute acalculous cholecystitis in a returned travel couple

A previously healthy 35-year-old Swiss woman presented with fever, headache, and myalgia for three days. Symptoms began on the final day of travel in Colombia. Abdominal examination revealed a positive Murphy sign. Laboratory results at presentation are shown in Table 1. Abnormal findings included a thrombocytopenia (121,000/mm), an elevated total bilirubin (48 μmol/liter), and high alkaline phosphatase (163 U/liter). Abdominal ultrasound showed signs of an acute acalculous cholecystitis (AAC) (Fig 1). At presentation, chest radiography showed no abnormalities (Fig 2A). On the third day of hospitalization, however, the patient developed a cough, dyspnea, and hypoxemia. A second chest radiography revealed a left-sided infiltrate (Fig 2B). Her traveling companion was admitted to the hospital with identical symptoms, including an AAC and development of pneumonia. What is your diagnosis?