Acute Eosinophilic Pneumonia

From HealthDay News via MedicineNet: Government Studies Rare Pneumonia Outbreak Among Iraq Troops.

[...] acute eosinophilic pneumonia (AEP), is so rare that the entire medical literature contains only about 150 published accounts of it, according to lead study author Dr. Andrew F. Shorr, chief of the pulmonary clinic at Walter Reed Army Medical Center in Washington, D.C. And none of that literature has accounts of the disease striking in clusters, as it apparently did in Iraq.
There seems to be no explanation for the unusual cluster, which included two deaths, except for one salient fact -- all of the patients were smokers, and nearly all of them were new to the habit.