Key Legionella Risks in Hospitals and Care Homes

The Legionella pneumophila bacteria is widely distributed in natural water sources and can also exist in soil. In low numbers, the bacteria do not cause a problem to most adults, but at higher concentrations Legionnaire’s disease, a potentially fatal form of pneumonia, may develop if the microbe is breathed in. This usually occurs through the inhalation of airborne water droplets which are contaminated with the bacteria. Legionnaire’s disease cannot be contracted from drinking water containing the microbe, nor is it passed on via human to human contact.

Conditions that encourage the growth of the bacteria include a water temperature of between 20°C and 45°C, the storage or re-circulation of water within a system and a source of nutrients on which the bacteria can feed, such as sludge or rust at the bottom of a dirty tank. Any water system which allows the creation of breathable droplets will also increase the threat of the disease. Therefore, water towers, particularly those associated with air conditioning and cooling systems, hot and cold water supplies such as showers, taps and sprays, and spa pools and hot tubs may all pose a risk. With the exception of the latter, these types of installations are clearly common in hospitals and care homes. Furthermore, these health facilities are often housed in old buildings or converted from buildings that were originally designed for another purpose. The water supply systems in such buildings may be complicated and, due to alterations, there may be disused lengths of piping and neglected storage tanks. When rooms are unoccupied for several weeks, stagnation of water in infrequently used outlets may also pose a problem.

The risk of developing Legionnaire’s disease rises with age but patients with chronic diseases, such as cancer or heart disease, an impaired immune system or a history of smoking are also particularly at risk. Many patients and care home residents will fall into at least one of these categories. Therefore, the combination of a potentially suitable environment for the survival of the bacteria and a particularly vulnerable segment of the population means that hospitals and care homes need to be especially aware of the potential threat of the disease.

What can be done to reduce the risk of Legionella infection? Firstly, in the UK it is a legal requirement for all business premises to conduct a Legionella risk assessment. This will help to identify any risks and suggest possible ways to manage them. Further steps might include:

• Ensuring that the water in all systems is at the correct temperature. Cold water should be below 20°C, to inhibit the growth of the bacteria. In hot water systems in hospitals and similar premises, water should be stored at a minimum temperature of 60°C and delivered to outlets at 55°C.
• Reducing stagnation by removing all unnecessary water tanks and keeping pipework length to a minimum. Any outlets that have not been used for at least a week should be run for five minutes before using.
• Reducing the possibility of aerosolization of water droplets by fitting taps with tap spout aerators. These prevent air from mixing with the water as it leaves the tap, so that contaminated aerosol particles cannot form.
• Keeping the system and the water within it clean via a programme of regular maintenance.
• Treating the water within a system. Possible treatments include ultra violet (UV) light treatment, which kills the bacteria, or using a reverse osmosis system to filter out particles and water-borne materials such as viruses. The advantage of both these options is that they are chemical-free, so will not leave a taste or residue in the water.

Along with an awareness of the potential hazards, these steps should help to ensure that the risk from the Legionella bacteria in hospitals and care homes is minimized.