A waterborne bacteria at Kaiser Permanente Santa Clara Medical Center has infected 18 people, prompting an investigation that infectious disease experts describe as “alarming.”
Most patients are recovering at home, Kaiser Permanente Santa Clara physician Dr. Rakesh Chaudhary told SFGATE. He added that the bacteria was identified during “robust routine internal monitoring processes” at the hospital, but the source of contamination remains unclear.
“Legionella bacteria occur naturally in water and are spread by inhaling contaminated mist, not through person-to-person contact,” Chaudhary said. “… Our medical center is a safe place to visit and receive care.”
Legionella bacteria can spread through large plumbing systems and air conditioning infrastructure. The pathogen became widely known after a 1976 outbreak among attendees at an American Legion convention in Philadelphia, which gave rise to the name Legionnaires’ disease.
The illness is a severe form of pneumonia that can trigger cough, fever, shortness of breath and gastrointestinal symptoms, including nausea, vomiting and diarrhea. In severe cases, it can lead to respiratory failure.
Although Chaudhary said the Kaiser facility remains safe and continues operating normally, Dr. Monica Gandhi, an infectious disease expert at UC San Francisco, said the number of cases was striking for a hospital setting.
“If there’s two cases, that is already a cause for real concern,” Gandhi said. “To get up to 18 cases in a hospital system is really quite alarming.” Dr. Peter Chin-Hong, another UCSF infectious disease expert, said the case count “does sound large,” though he cautioned that the number could also reflect a thorough public health investigation.
“Sometimes large numbers reflect thorough investigations,” Chin-Hong told SFGATE. “It’s hard. I would want to know how sick were these people who were found.”
Hospitals can be particularly vulnerable to Legionella because they care for patients who may be at higher risk of severe illness. They also have complex plumbing and cooling systems where the bacteria can grow, and they are capable of producing the mist in which it spreads.
Kaiser has not publicly disclosed whether the 18 cases involve patients, employees or visitors. Gandhi said that gap matters because Legionella can be most dangerous in people already receiving hospital care.
“The worst possible place for Legionella to spread is a place where people are being hospitalized and immunocompromised,” Gandhi said, adding that these groups of people are more likely to experience more severe symptoms.
Symptoms of Legionnaires’ disease can resemble other forms of pneumonia, including fever, cough and shortness of breath. The disease can also cause gastrointestinal symptoms such as nausea, vomiting and diarrhea, according to the California Department of Public Health.
Chin-Hong said the infection can be difficult to immediately identify because symptoms are often nonspecific. “It just looks like any bad pneumonia,” he said. “Knowing that there’s an outbreak is important for providers in the community to think about Legionella in their patients.”
Out of an abundance of caution, Chaudhary said Kaiser has since completed “additional water treatment measures and preventive measures” while continuing to test its water systems in coordination with local and state public health authorities. Most healthy people exposed to Legionella do not get sick, the CDPH wrote, but preventing illness depends largely on controlling the bacteria in water systems before it spreads.
