Legionella – not evolving just opportunity accepting

Last week the CDC in the USA reported that:

Two things caught my attention with this report, firstly it was tragically an infant – although all Legionnaires’ disease fatalities are tragedies - and not the typical demographic for the disease and secondly it is another potential system to add to an increasing list of risks.

Susceptible populations

Notwithstanding a small number of very rare birthing pool related legionellosis, neonates and infants are not prone to the disease. Indeed, globally the World Health Organisation (WHO) identify for Legionnaires’ disease:

• 75-80% of reported cases of are in people over 50 years old,
• The majority of which (60-70%) are male; and
• The death rate is 5%-10%.

These would be figures we’d recognise in the UK too from the published surveillance figures. What the figures don’t say however, is that across Great Britain, Europe and the US, numbers of reported cases are on the increase.

Susceptible systems, services and equipment 

For most, when you mention Legionella, hot and cold water systems and evaporative cooling towers are the two systems that spring to mind and for good reason. Hot and cold water systems, particularly in the UK are responsible for most outbreaks, whereas evaporative cooling systems, by their nature being far more indiscriminate, lead to very big outbreaks.

Under these however, we are seeing an increasing list of systems, services and equipment linked to Legionella contamination and cases of Legionnaires’ disease. These have been reported to include:

• Spa pools/hot tubs (including non-natural onsen)
• Pressure/spray washers
• Car washes
• Machine tools using water (e.g. jet cutting)
• Irrigation and sprinkler systems
• Medical and dental equipment (e.g. ventilators, CPAP machines, bronchoscopes, dental scalers)
• Vehicle windscreen washers
• Ice machines
• Retail misting systems
• Potting compost
• Agricultural/horticultural misters and sprayers
• Air washers
• Effluent treatment plant
• Solar thermal systems
• Harvested water systems
• Water features/ornamental fountains
• Sprinkler and hose reel systems
• Water based dust, fire and odour suppression systems
• Ultrasonic foggers/humidifiers
• Emergency showers/eye baths

This list is not exhaustive but does highlight the extent and breadth of the risk. In all instances though, four primary conditions exist:

1. The water in the systems is capable of becoming contaminated with Legionella;
2. The systems do or are capable of holding water at between 20°C and 45°C;
3. The systems can hold/retain/recirculate that water and potentially allow for it to stagnate;
4. The systems generate fine (breathable) droplets of water/aerosols.

Mechanical showers are probably the oldest of these systems and services, although they in reality are a relatively recent invention (c250 years), many of the others are much later (late 20^th or indeed early 21^st century). Our increasingly complex use of water, coupled with changes in climate, lifestyle and demands appears also to be selecting for Legionella. It is after all an opportunistic pathogen (disease causing organism) and if we give it the opportunity.

What also remains true is that we understand very well how it causes disease and we should therefore be able to successfully manage it. Having been supporting organisations to manage Legionella risk for 37 years and acted as a retained expert in a number of investigations and prosecutions (none of them customers at the time I hasten to add), it is no accident why there are those who manage Legionella very effectively and other who do not.

Risk assessment, schemes of control and training are all common threads as to where things go wrong, but in nearly every case the documentation is the over-riding factor, “logbook” mentality leads to logbook thinking and that creates gaps. Whereas “management system” mentality leads to management system thinking and that usually drives not just control, but compliance.