Fountains and water walls can be sources of calm, of negative ions that improve the moods of those around them.

But they can also be fonts of a dangerous bacterial disease, especially in hospitals, public health disease investigators in Wisconsin are reporting.

In a new study, staff of the Wisconsin Division of Public Health detail how eight people contracted Legionnaires' disease from tiny bacteria-laced water droplets sprayed from a water feature in the lobby of a hospital.

None of the people were in-patients; three were there for medical appointments, three were picking up prescriptions at the pharmacy, one was a delivery person and one was waiting for a relative who had an appointment.

Yet in as little time as those activities took, the eight were infected with Legionella bacteria which causes Legionnaires. All needed to be hospitalized, though all eight recovered.

'Fountains and health-care facilities don't mix'—Dr. Thomas Haupt

The outbreak happened in March 2010 at Aurora Hospital in Cudahy, Wis., which is just south of Milwaukee. The incident is described in a study that will be published in the February issue of the journal Infection Control and Hospital Epidemiology.

"Fountains and health-care facilities don't mix," lead author Thomas Haupt, a respiratory diseases epidemiologist, said in an interview from Madison, the state capital.

Haupt said there was a previous report of a hospital patient being infected with Legionnaires after repeatedly passing in front of a water wall at a National Institutes of Health hospital in the Washington, D.C. region. But this may be the first where the people infected were not even patients of the hospital.

Outbreaks of Legionnaires aren't uncommon in hospitals and long-term care facilities, but having patients come in with the disease and having them admitted to two different hospitals was initially perplexing.

Once investigators realized six of the patients remembered spending time in the lobby of Aurora Hospital, however, things started falling into place fast.

Legionella bacteria are ubiquitous, at low levels, in water. Under the right conditions colonies of the bacteria can multiply to dangerous levels. Previous outbreaks have been linked to air conditioning units, shower heads and other settings where water is aerosolized.

A fountain in which water gets recycled through a closed system and water temperatures rise to Legionella-friendly levels —25 to 42 Celsius — provides just such a setting.

Water samples taken from various locations in the hospital and from the water wall pinpointed the latter as the source of infection, the study says.

In this case, pieces of foam were the problem. The water feature had a tiled wall down which water flowed; the water collected in a trough filled with decorative rocks at the base of the wall. The rocks rested on a bed of foam-like material. Flood lights located over the feature and in the trough had the effect of heating the water, as did a fireplace that was located on the reverse side of the water wall.

Testing showed the foam was heavily contaminated with Legionella bacteria.

Foam difficult to disinfect

"They did great routine maintenance at the facility, but again the foam could not be decontaminated. Because it's a semi-porous type of foam, that little bit of moisture stays in there and with the heat the Legionella just continued to grow to very large amounts," says Haupt.

His team looked for other people who might have had the illness, but didn't turn up additional cases.

Not everyone exposed to Legionella bacteria will go on to develop Legionnaires' disease. But smokers and people who have underlying illnesses — HIV, heart disease, diabetes and the like — are at increased risk, which explains why outbreaks are often seen in hospitals and long-term care facilities.

Haupt says his department now advises hospitals and other health-care facilities against fountains and other decorative water features.

Dr. Allison McGeer, head of infection control at Toronto's Mount Sinai Hospital, says her hospital has a water feature in its emergency department. But the feature is enclosed.

"It's sealed — for precisely that reason, because anything that generates aerosols around patients poses a risk for Legionella," McGeer says.

"It's not open to the air anywhere in the emergency department."

McGeer says there have been a number of Legionnaires outbreaks associated with aerosolized water — a flower show in the Netherlands where flowers were sprayed, grocery stores where fruit and vegetables were misted to keep them fresh, and a hotel with a fountain in its lobby.

"There are, I think, good reasons why people like water features," she says. "But there are also good reasons why we don't have them in hospitals."