Symptoms may include fever, coughing, chest pains, breathlessness and diarrhoea but, of course, diagnosis must be left to medical professionals, who are required by law in South Africa to notify the National Institute for Communicable Diseases (NICD) whenever they detect any cases of legionnaire’s disease. According to the World Health Organisation, the incubation, period is between two and 10 days, and about 15% of infected people die. This is serious.
Legionnaire’s disease does not just happen. Falling prey to this nasty pathogen is the result of a series of events. According to the NICD, transmission is predominantly associated with warm, artificial and engineered water systems that provide the three conditions needed for transmission: heat, stasis and aerosolisation. In simple English that means Legionella thrives in warm, standing, still or stagnant water, and it is transmitted in the droplets that occur when water is aerosolised. In other words, infection is the result of an unbroken chain of events.
- First, the bacterium must successfully enter the water.
- Then, assuming the lurgy managed to get past any initial barriers you may have installed, it will need to breed sufficiently to become a threat. For this it needs nice warm, stagnant water of between 20˚C and 45˚C. Remember, in warm climates, Legionella can live and be transmitted in ‘cold’ – or rather unheated – water that is quite likely to be over 20˚C.
- Then it needs to be aerosolised, and, until you stop to think about it, we don’t realise how much aerosolised water is about – think of showers, the splashing in heated pools, ornamental water features, spa baths, etc.
- And then it needs to be breathed in through the aerosolised droplets by a person who is sufficiently tired, immune
compromised, or just unlucky, to be unable to resist infection.
Eeek! So what do you do?
‘Preventing legionnaire’s disease is a matter of breaking the chain described above,’ says Jay Moodley, operations director of water hygiene risk management consultants, Ecosafe. ‘Unfortunately,’ he continues,
“While some countries, like the UK and the USA (where the disease was first identified) have well-defined public health protocols for prevention and detection, the legislation in South Africa is a tad vague – and is mostly covered under the Hazardous Biological Agents (HBA) regulations of the Occupational Health and Safety Act (Act 85 of 1993).”
In 2013, this was supported by the development by the SABS of a South African standard specific to Legionella control. It’s well worth getting a copy – SANS (South African National Standard) 893 (1 & 2).
Legionella is not something you deal with at the design stage, and then forget. It requires permanent vigilance and a dedicated maintenance strategy.
There are specialist consultants who are well versed in the prevention, detection and elimination of Legionella outbreaks, and almost every hotel group, cruise line, gym group, hospital group, and – yes – residential estate has systems in place to protect their guests, clients and/or residents. So, what follows is probably nothing new, but it bears repetition.
UV radiation of all water entering the system is a good first barrier, but it may not be 100% effective, so the two main preventive strategies are to reduce stagnation, and to ensure water is kept below or above the temperature in which Legionella thrives. The hot-water system is usually the most risky, so the most obvious precaution is to store hot water at or above 60°C, and to deliver it to users at a minimum of 50°C. It is also a good idea to install a ring main to keep hot water moving steadily and constantly through the building – this also reduces electricity bills. If you are doing any remodelling of plumbing systems, ensure that you don’t leave any ‘dead legs’ or uncapped pipes, as these can become icky stagnant reservoirs of all kinds of nasty things – including, possibly, Legionella.
It’s usually easier for cold-water systems, where the safe temperature in storage tanks is anything below 20°C, but in the warmer parts of the country, unheated water can easily reach, and exceed, 20°C. Also, it’s important to keep all storage tanks covered to prevent contamination. And, remember, Legionella likes water that remains uncirculated for long periods, so keep all stored water moving.
Other possible strategies include:
- the use of biocidal metal ions like copper or silver
- ozone treatment
- installing ultraviolet (UV) radiation at the point of entry
- periodic pasteurisation by heating the water to 70°C for 24 hours, and then flushing all the taps in the system
- regular visual inspection
- regular maintenance procedures like periodic draining, descaling and cleaning of hot-water storage tanks.
But, despite all these precautionary measures, it is still necessary to do regular checks. You should send water samples to an independent, accredited laboratory for assessment at regular intervals. Many organisations – for example, all Marriott hotels worldwide – do monthly tests as part of their routine Legionella management programme. This is, according to Moodley, the gold standard, or best practice, but you could safely do it less frequently if based on a site-specific Legionella risk assessment and tailor-made policy.