Seattle Children's Hospital has revealed that one patient has died and five others have been infected by a potentially dangerous mold that has forced the medical center to close all of its main operating rooms. The hospital disclosed the infections and death to The Seattle Times Tuesday in response to follow-up questions regarding the closures of four operating rooms on its main Seattle campus May 18 because of Aspergillus mold and of the remaining 10 operating rooms May 24.

The hospital says operating rooms have been infested by mold -- off and on -- for about a year likely because of deficiencies in the operating rooms' air handling and purification systems.

"We are deeply saddened that one of our patients died after developing an Aspergillus infection in 2018," Seattle Children's public relations manager Alyse Bernal told CBS News Tuesday in a written statement. "We want to reiterate that the risk of developing an infection for patients is very low."

Upgrades, but not ready yet

Bernal said the hospital had "identified deficiencies in our air handlers, including gaps in the air filtration system that we believe to be key contributing factors to the air quality issue," and in collaboration with outside experts had replaced one air handing system, installed a new humidification system, added an extra step to operating room cleaning protocols that uses ultraviolent light to disinfect surfaces, and sealed leaks in the ventilation system.

She said the hospital would "reopen our operating rooms when we are confident they are safe for patient care," but she did not give a time frame for that to happen.

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"We are very sorry for the impact the air quality issue in our operating rooms has had on our patients and families, and we are taking this situation very seriously," Bernal added.

Spokesperson Lindsay Kurs added in a subsequent statement, also emailed to CBS News, that Seattle Children's was continuing to "postpone or divert some surgical cases and move others to our Bellevue campus," but noted that doctors were still carrying out operations "in other areas of our hospital that have been determined to be safe for surgical care, like our cardiac catheterization facility."

Kurs said the hospital was "closely collaborating" with four other healthcare facilities in the area, "so that children in our region may continue to have access to the pediatric surgical services they need."

About 1,000 surgeries have been postponed, while more urgent procedures have been moved to either Seattle Children's other campus in Bellevue, or the other regional hospitals.

What is Aspergillus mold?

Bernal wrote in an email earlier that three patients were infected last year and three this year. The patient who died developed the infection in 2018.

"The six patients who developed Aspergillus infections were at higher risk of infection due to the types of procedures they had," Bernal said. "We are deeply saddened that one of these patients died."

Aspergillosis mold is seen growing in a dish in a file photo iStockphoto

No other information about the children and their conditions was released.

The Centers for Disease Control and Prevention has said Aspergillus mold can live indoors or outside and that most people breathe it daily without getting sick. But people with weakened immune systems are at a higher risk of developing infections in the lungs or sinuses from the mold. Aspergillosis can range from mild to serious, manifesting as an allergic reaction or infections in the lungs and other organs.

Last summer, after air testing at Children's detected the mold in two operating rooms and an equipment-storage room, those rooms were closed for three days and all operating rooms and storage rooms were inspected, Bernal wrote. "At that time, the issue appeared to be confined to the affected rooms and we took appropriate corrective actions," she wrote.

Children's also reached out to Public Health - Seattle & King County, which connected the hospital to the CDC because the federal agency had more expertise dealing with that kind of mold, public health spokesperson James Apa said. The CDC issued no report after it determined Children's was taking appropriate actions to investigate and address the problem, Apa said. Washington state Department of Health investigators also checked out the hospital and offered suggestions on how to improve air quality, which the hospital followed, Bernal wrote.

But the mold returned in 2019. In May, it was detected in four operating rooms and some equipment-storage rooms during a routine check, Bernal said.

After the hospital closed the four operating rooms May 18, some "urgent and less invasive procedures" were performed in the remaining 10 operating rooms, Bernal wrote in an email to The Times Tuesday.

Six days later, those operating rooms were also closed. Bernal said the additional closures were needed so crews could access and fix the hospital's air system. She would not say whether mold was detected in those rooms.