What precautions should hospitals take to prevent legionella outbreaks?

Hospital Precautions for Legionella Prevention

Hospitals should implement a comprehensive water management program that includes maintaining hot water temperatures above 51°C (124°F), cold water below 20°C (68°F), and regular cleaning and disinfection of water systems to prevent Legionella outbreaks. 1

Water System Management

Temperature Control

• Maintain potable hot water at a minimum return temperature of >51°C (>124°F) and cold water at <20°C (<68°F), especially in facilities housing organ transplant recipients or other high-risk patients 1
• Use thermostatic mixing valves to prevent scalding when maintaining high water temperatures 1
• Temperature control is one of the most effective methods for reducing Legionella concentrations in water systems 2

Chemical Treatment

• For hospitals with high-risk patients, chlorinate heated water to achieve 1-2 mg/L (1-2 ppm) of free residual chlorine at the tap 1
• Use EPA-registered biocides for water treatment, though the effect may last only a few months and require regular application 2

Regular Maintenance

• Remove, clean, and disinfect shower heads and tap aerators monthly in areas with high-risk patients using a chlorine-based, EPA-registered product 1
• If an EPA-registered chlorine disinfectant is not available, use a chlorine bleach solution (500-615 ppm [1:100 v/v dilution]) 1
• Clean hot-water storage tanks and water heaters regularly to remove accumulated scale and sediment 1

Cooling Tower Management

Design and Location

• When constructing new healthcare facilities, locate cooling towers so that drift is directed away from the air-intake system 1
• Design towers to minimize the volume of aerosol drift 1

Maintenance and Monitoring

• Install drift eliminators to reduce aerosol spread 1
• Use effective EPA-registered biocides on a regular basis 1
• Maintain cooling towers according to manufacturers' recommendations 1
• Keep detailed maintenance and infection-control records, including environmental test results 1

Surveillance and Testing

Environmental Surveillance

• Periodic culturing for Legionella in potable water samples from hematopoietic stem cell transplant (HSCT) or solid-organ transplant units should be performed as part of a comprehensive prevention strategy 1
• Consider routine sampling for Legionella in hospital water systems, particularly in centers with transplant units or immunocompromised patients 3

Clinical Surveillance

• Maintain heightened awareness of hospital-acquired Legionnaires' disease with appropriate laboratory diagnostic facilities 3
• Maintain a high index of suspicion for legionellosis in transplant patients even when environmental surveillance cultures do not yield Legionella 1

Special Precautions for High-Risk Units

If Legionella is detected in the water of a transplant unit, implement these measures until Legionella is no longer detected:

1. Decontaminate the water supply through superheating (raising water temperature to 71-77°C/160-170°F) or hyperchlorination 1
2. Do not use water from faucets in patient-care rooms to avoid creating infectious aerosols 1
3. Restrict severely immunocompromised patients from taking showers 1
4. Use water that is not contaminated with Legionella for HSCT patients' sponge baths 1
5. Provide patients with sterile water for tooth brushing, drinking, and for flushing nasogastric tubing during outbreaks 1

Response to Confirmed Cases

For Facilities with Transplant Recipients

• When a case is confirmed, conduct a combined epidemiologic and environmental investigation to determine the source of Legionella 1
• Contact local or state health department if assistance is needed 1
• If the facility's potable water system is the source, implement special precautions for high-risk patients and decontaminate the water supply 1

For All Facilities

• If cooling towers or evaporative condensers are implicated, promptly decontaminate the cooling tower system 1
• Assess the efficacy of implemented measures by collecting specimens for culture at 2-week intervals for 3 months 1

Common Pitfalls and Caveats

• Relying solely on one prevention strategy may be insufficient; combining temperature control, water quality improvement, and chemical disinfection is most effective 2
• The effect of biocides may be temporary, requiring regular application 2
• Failure to maintain adequate records of water system maintenance and testing can hamper outbreak investigations 1
• Do not use large-volume room air humidifiers that create aerosols unless they undergo high-level disinfection and are filled only with sterile water 1
• Even with proper maintenance, Legionella can be part of the normal ecology of a public water system and may be detected in regulatory-compliant drinking water 4