A 45 y/o male is admitted from the ED with c/o of dyspnea, d…

A 45 y/o male is admitted from the ED with c/o of dyspnea, dry cough, fever with onset 24 hours ago and has worsened.  Vital signs, HR 108, RR 28, SpO2 89% on Room Air.  CXR shows patchy infiltrates bilaterally. The patient has a positive history of smoking and is currently working as a building renovation contractor in a local hotel’s spa and pool area.   What is the most likely cause of his acute illness?