A 65 year-old man presents to the hospital with a one week history of malaise, headache, fever, and chills. He is admitted and over the next week his disease progressed with a worsening cough and shortness of breath. His physical exam was benign except for pulmonary compromise. The patient is current on all of their vaccinations and has no recent travel history. A chest radiograph showed multilobar infiltrates. Other significant laboratory findings include an elevated white blood cell count with increased polymorphonuclear neutrophils. Because the patient had a prior history of drug abuse and alcoholism, a toxicology screen and HIV serology were performed. Both were negative. A bronchoscopy was performed, with a bronchoalveolar lavage (BAL) showing many white blood cells, but no organisms. Calcofluor white stains for fungi and direct fluorescent-antibody stain (DFA) for Pneumocystis were also negative. Routine bacterial culture of the BAL was negative.