Legionnaires’ disease, also called Legionellosis, is a severe and potentially fatal type of pneumonia. It is contracted by inhaling water vapour or steam containing the Legionella bacteria, which is very likely to happen when taking a hot shower.

The bacteria love warm, stagnant water. They can grow in water temperatures ranging 20 – 45^oC and thrive in the range of 32 – 44^oC, which commonly occur in plumbing systems, spa pools, hot water tanks and evaporative condensers of commercial AC systems. However, Legionella bacteria cannot grow at higher temperatures and are killed almost instantaneously at around 70^oC.

This is why the District Health Board is sending a warning against turning down hot water cylinders in an attempt to save money. For the same reason, the Building Code also requires hot water systems to have the storage water heater thermostat set to a minimum of 60^oC.

This warning should not be taken lightly. Legionnaires’ disease can lead to respiratory failure, septic shock or complications that may result to organ failure or even amputation, which was sadly the case for two people in Hawke’s Bay in 2015.

Facts about Legionellosis

• The illness is caused by Legionella strains, particularly pneumophila and L. longbeachae, which are ubiquitous in the New Zealand environment. They are found in both potable and non-potable water systems, and can easily find their way into engineered water reticulation systems.
• Hot water cylinders are a breeding ground for the Legionella bacteria, as are boiler systems, water-cooling towers, garden hose-pipes, air conditioners and even mist sprayers in the grocery store produce section. Legionella can also survive in some soils or composts.
• Legionella bacteria cannot be contracted by drinking contaminated water nor transmitted from one person to another.
• In healthy people, the disease manifests as a very bad cold with symptoms including high fever, chills, headaches, muscle aches, loss of appetite, cough and occasionally diarrhoea. But for those with immature or impaired immune systems (i.e. children, older people, smokers, alcoholics, cancer patients, etc.), the effects can be much worse and fatal.
• A mild form of Legionnaires’ disease, known as Pontiac fever, doesn’t affect the lungs and usually clears within two to five days without treatment.
• Although the bacteria primarily target the lungs, it can also cause infections in wounds and other parts of the body.
• Some infected people will suffer long-term health issues such as fatigue, neuromuscular and neurologic symptoms.
• The legionella bacteria primarily spread through micro water droplets, but it can also be transmitted via aspiration of contaminated water or working with contaminated soil.

Are you safe from Legionellosis?

Homes and workplaces are generally safe. But as a homeowner, it is your duty to undertake regular maintenance of your water systems. Workplaces are also required under legislation to comply with building maintenance guidelines, especially those with cooling towers.

Many infections are without symptoms as healthy adults have antibodies to the bacteria, showing evidence of previous exposure. Only a small number of cases will have had an illness with symptoms.

What can you do to minimize your risk?

Prevention should always be the first course of action.

1. Since Legionella bacteria cannot survive in water at 60^oC or above, you should keep your hot water cylinder at a minimum temperature of 60^o
2. For households with a roof collected tank water supply or other non-reticulated water supply, the water tank must be maintained according to the guidelines.
3. When working with potting mix, soil or compost, wear a mask to avoid inhaling dust. Dampen the soil to avoid stirring up the dust too much.
4. Installing tempering/mixing valves are recommended to ensure safe water temperature at the tap. To prevent burns and scalds, water tap temperature should be no more than 45^oC for children and no more than 55^oC for adults.

For more information about keeping your water systems safe, contact our team at 0800 429 546.