Tackling Legionella: How to assess and minimise your risk
Tackling Legionella: How to assess and minimise your risk

By Rory O’Malley – Hydraulic Principal/Senior Hydraulic Designer.

I recently heard of some health care facilities in Australia that are removing their drinking water fountains and supplying their patients and visitors with bottled water in order to prevent the spread of Legionella.

Is this really a necessary step? Or have we gone too far?

If you’ve had any dealings with health or aged care projects of late, you’ll have no doubt noticed that design methods which control the spread of Legionella within water distribution systems is fast becoming a top priority. Unfortunately, along with this increased interest, there seems to be a lot of white noise discussion and general confusion about what Legionella is and how it actually spreads. So firstly, lets clear up exactly what Legionella is.

What exactly is Legionella?

Legionella is a type of bacteria which is naturally present in the environment. It’s usual habitat is fresh water and the microbe can be found in lakes and streams. They live inside of other microbes called amoebae and protozoa, which are small one-celled organisms. These microbes provide nutrients for Legionella to grow and replicate, as well as a shelter that protects Legionella from adverse environmental conditions such as extreme temperatures and chemicals like chlorine.

There are over 60 species of Legionella bacteria with only a few of them known to cause human disease. The most common infections are Legionella pneumonia (a serious lung infection causing cough, fever, and headaches, which can sometimes be fatal) and Pontiac fever ( a self- limited viral like illness causing muscle aches and fever). The species most commonly known to cause infection in humans is Legionella pneumophila.

How does it spread?

Legionella is generally not present in high enough numbers in the natural environment to cause disease. Infection is more commonly seen in association with man-made watering systems such as water heaters and cooling towers. These systems, if not designed properly, can provide optimum conditions for Legionella to multiply. From here, the bacteria causes disease by entering the lungs through inhalation of aerosolized water particles. Despite this, only a small number of people exposed to Legionella in this way will become sick.

Legionella poses the biggest risk to the following groups as outlined in the Queensland Public Bill 2016:

  • Severely immunocompromised patients and some patients receiving high doses of immunosuppressive medication.
  • People with chronic underlying disease such as diabetes mellitus, chronic liver failure, chronic renal failure, congestive heart failure, HIV/AIDS and some forms of cancer.
  • Smokers, people with excessive alcohol intake and people over the age of 50 years.
  • People who have undergone recent surgery, intubation and mechanical ventilation.
  • People who have aspirated foreign matter into their respiratory passages.
  • People who have used respiratory therapy equipment such as nebulisers.

Many of the people who fit these criteria are found in aged care and hospital facilities, which is why they have such a strong emphasis on Legionella control.

Why does recontamination sometimes occur?

We often hear of facilities who have recurrent problems with Legionella outbreaks, despite their best efforts to eradicate the bacteria.

The main reason for re-contamination is due to the Legionella bacteria’s ability to form biofilmA small number of known bacteria are able to form this extracellular matrix which is secreted into the environment as a nutrient-rich ‘slime’. This biofilm protects the bacteria from environmental damage such as chemicals and antibiotics and usually begins to form when free-floating Legionella bacteria attach onto a surface such as a water pipe. The most commonly known example of a natural biofilm is the formation of plaque on animal teeth.

Biofilms are notoriously difficult to remove from surfaces and the bacteria within these complexes are even harder to destroy. They can often be a source of re-seeding and recontamination within water systems if not treated correctly.

What causes a Legionella outbreak, and how can you control it?

When we think of a Legionella outbreak, we generally assume the outbreak developed from optimal warm water temperatures between 32 to 42 degree Celsius. While this is true, a properly designed hot water system will prevent an outbreak. So, what causes it, and how can you control it?

1. Control the domestic cold water supply rather than the reticulated hot water:

One of the main risk sources for Legionella is actually from incoming, uncontrolled cold-water supply from towns water infrastructure. When towns water mains supply a site, the water needs to be immediately controlled of any microbial traces before infecting the downstream water network. This initial control will flow downstream to the facility and ensure the water supply is properly controlled from the start.

2. Hydraulic Design 1%ers

In simple terms, if you keep reticulated hot water ‘very hot’ (above 60 degrees) and cold water ‘cold’ (below 20 degrees), you are preventing the conditions that can support bacterial growth.

If water is stagnated, this can lead to starving the biofilm of nutrient supply. Once water starts moving again, the biofilm reseeds into the pipework to spread Legionella throughout the water system. The more complex/controlled the water system is, the more risk there is for associated issues with incorrect installation and future additions to the system.

Design of hydraulic systems needs to use these simple ‘one percenters’ which all add up to significantly reduce the spread of Legionella. These include:

  • No deadlegs and installation of copper pipework to significantly reduce biofilm buildup.
  • No cooling towers (this is the most common source of legionella).
  • No spas, chilled water machines, dental chairs, flexihoses, or aerators in taps.
  • No airators on tapware in apartment. This measure reduces risk of spreading particles through the air.
  • Keep pipework run under 6 meters from any Thermostatic Mixing Valve (TMV) warm water line to a fixture e.g. keep the shower and basin as close as possible to a single TMV.
  • Hot flushing procedures of water over 60 degrees to all TMVs in accordance with the water risk management plan.
  • Keep existing building services drawings regularly updated to minimise confusion within the facility.

What can you do to reduce Legionella risk?

Firstly, there is no need to panic and remove all your water fountains. Instead, the best way to reduce your risk of outbreak is to develop and implement a WRMP (Water Risk Management Plan).

All government organisations already have their own WRMP. Hopefully if you run or manage a private health facility, you also have in place a well-planned and comprehensive WRMP. If not, then you need to develop some guidelines for your WRMP that are specific to your facility.

These need to encompass the international World Health Organisation guidelines, the national Australian government Enhealth Legionella control guidelines and your relevant state Public Health Act (for example, in Queensland we have the Public Health Act for Water Risk Management Bill 2016). Remember to ‘look at yourself’ rather than simply copy other health care facilities.

The cause of an outbreak can sometimes be nearly impossible to prevent. If you do get an outbreak, an effective WRMP will focus on how to quickly isolate and stop further spread. It will also help you plan and prepare for any legal consequences, business disruption, and productivity loss, which can be significant if you are non-compliant. Within the next two years, mandatory testing of private facilities across Australia to check for compliance is set to occur. Those in Australia’s southern states will be well prepared, with 90% of organisations already having WRMP’s in place in order to protect residents, patients and visitors, and reduce potential litigation, should an incident occur.

Key takeaways:

1. Ensure a facility specific WRMP is implemented and strictly adhered to.

2. Implement a simplified building services design in accordance with facility water risk management plan.

3. Make Legionella control a high priority for any health or aged care facility.

References and further reading:

National enHealth Guidelines for Legionella Control – in the operation and maintenance of water distribution systems in health and aged care facilities.

Queensland Health Legislation for water risk management in healthcare and aged care facilities.

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