Dr. Bégué helped treat Zachary and asked for a review of infection control procedures regarding his treatment, but did not consider opening a wider inquiry, he said later.

While Zachary had been struggling, another premature baby received a diagnosis of mucormycosis and died in a different part of the hospital, but Dr. Bégué did not learn of the case. In late June, Tierica Jackson, 10, admitted for heart surgery, also fell victim to the infection. Hospital personnel began swabbing various surfaces to determine the source, which struck one more patient, an 11-year-old girl, who died the day after her diagnosis. One of the doctors decided to test the linens.

A Prime Environment

Fungi thrive in moist environments, and the 40,000-square-foot washing warehouse owned by the hospital’s off-site launderer, TLC Linen Services, was just that. The laundry sits several blocks from Lake Pontchartrain on a dirt road in the city’s Ninth Ward.

The owners, who declined interview requests, replaced drywall and flooring after the levee failures caused by Hurricane Katrina brought in water. But he never tested to verify that the plant was free of mold, records showed.

The company, which was not accredited by the main voluntary group that inspects health care laundries, also lacked proper filters on ventilation fans to block spores and dust from the street, records showed. There was also reason to suspect that the outbreak was due to myriad problems with the way hospital workers handled linens, court documents showed. (Three patients’ families have filed lawsuits; one was settled.)

In the rare instances when linens have been associated with transmitting illnesses, the problem is usually caused by improper transportation or storage, said Lisa Waldowski, an infection control specialist with the Joint Commission, the organization that accredits most American hospitals. Hospitals typically do not sterilize linens, except those used in operating rooms. Hospital bedsheets and towels typically are washed and bleached to reach the same standard of cleanliness as hotel laundry. One key difference is that medical linens are supposed to be wrapped in bags or cellophane for transport.

Starting in 2007, TLC managers complained in meetings and emails about how Children’s Hospital housekeepers were handling the linens. Washcloths were being used as “cleaning rags” to wipe down bathrooms, TLC said. Laundry workers had to fish bags of dirty towels and sheets out of hospital trash bins. Trash was being put in linen carts and linens in trash carts.