A slow-brewing epidemic of a little-known, potentially fatal bacterial infection appears to be building among cardiac-surgery patients. The physicians who write the blog Controversies in Hospital Infection Prevention—all three of whom work at the University of Iowa—are so concerned about it that they are publicizing one of their own patients (within the bounds of medical privacy) to alert the rest of medicine.

The infection is Mycobacterium chimaera, which does not normally cause disease in humans, but is found in water and soil. The source is troubling and odd: spray from the fan of a heater-cooler device used to control the temperature of blood during a cardiac bypass, which contaminates both the otherwise-sterile operating field, and also any implants—a new valve, a vascular graft—being placed in or around