GP’s warning about Legionnaires
Every year or two, Legionnaires’ disease (LD) dominates headlines as another ‘‘outbreak’’ occurs – as we are seeing now in Canterbury with more than 10 people infected last week, and 21 during October.
This is undoubtedly a public health concern, as large numbers of affected people require hospitalisation and there is a reasonably high mortality rate.
However, what we now realise is infections with the legionella bacteria (responsible for LD) are more common than we thought and are probably responsible for many cases of pneumonia all year round. There were 271 notified cases of confirmed LD last year, but experts suspect the number is much higher. About 30 per cent of those who require hospital treatment end up in intensive care, many of them on life support – this is potentially very serious.
How to prevent being exposed to the infection, and what should you do if you think you have any of the symptoms
There are about 35 species of legionella, but the most common is legionella pneumophila. It is found in natural water supplies and soil, but can also live happily in water supply systems, such as hot water tanks, industrial air-conditioning units and spa pools. If the conditions are favourable it can breed rapidly, especially if water is either stagnant (through not being used frequently) or has debris in it. The ideal temperature for legionella to breed is 25-45 degrees Celsius and it is unlikely to survive temperatures above 60.
The risk of infection comes when you breathe in water or soil particles that contain large numbers of legionella bacteria. You cannot contract the infection through drinking infected water. Keeping water moving, and at temperatures either above 60C or below 20C, is a good way to reduce your risk at home, although there is a risk of scalding with water at 60C so ideally you should try to fit a ‘‘mixer’’ to ensure your water is heated to this temperature to reduce the risk of infection but comes out of the tap at a safer temperature (under 55C). If you have a spa or swimming pool, being rigorous about your water purification and testing is essential.
However, as only a third of our cases of LD are thought to be water-borne, soil is the more worrying problem. We suspect the spike in cases every spring is because of enthusiastic gardeners getting outside, using compost and potting mix. If these products have been breeding grounds for legionella (especially if they have been sitting round in a warm sunny spot for a while), inhaling even a few particles when opening the bag or spreading it onto your vege patch can be enough to put you at risk of serious infection.
I would recommend not only good gardening gloves for this job, but also a face mask to cover your nose and airway.
We know that many people who are exposed to legionella bacteria will be fine and develop no symptoms at all. But this is not the case for everyone, unfortunately.
Some will be unlucky and become seriously unwell or even die from their exposure. Some people are more vulnerable to begin with – older people and smokers should take care as they’re at greater risk.
❚ Dr Cathy Stephenson is a GP and a forensic medical examiner.
We suspect the spike in cases every spring is because of enthusiastic gardeners getting outside.