Legionella statistics and what they tell us
The Government has this week published information for householders on Legionella sampling in an unexpected move to make homeowners more aware of the importance of maintaining a safe and hygienic domestic water system. Coupled with the statistics on the occurrence of Legionnaires’ disease in 2015 which have also just been released by Public Health England, it paints an interesting and worrying picture of the impact of Legionella on our society.
It’s not clear why the authorities have decided to release information for homeowners right now, but there are perhaps clues in the statistics. After the rate of Legionnaires’ disease halved in the five years from 2006 to 2011 (down to around 250 diagnoses), cases per year are now steadily rising again and in 2015 were just shy of 400 people.
First, let’s look at some of the possible reasons behind the rise in cases.
Weather patterns show that our climate is becoming warmer and wetter. Scientific studies prove that the occurrence of Legionnaires’ disease increases with higher rainfall and when temperatures rise too it encourages Legionella bacteria to flourish (water held at between 20°C and 50°C is the perfect environment for it to multiply). Higher rainfall also increases the chance of flooding, which offers the bacteria an easy way in to a domestic water system, from its usual habitat in natural bodies of water such as lakes and rivers. As the chart illustrates, the stark difference in cases during the last quarter of the year versus the same period in 2014 and 2013 could be partially attributed to the exceptionally warm winter we experienced in 2015.
High risk groups
Legionella bacteria is more likely to trigger Legionnaires’ disease in certain groups of people, including those over 45 (and in particular those over 60), people with underlying health conditions such as diabetes or heart disease, smokers, heavy drinkers and anyone with a compromised immune system (such as people undergoing chemotherapy). While rates of drinking and smoking are decreasing, all the other high risk groups are on the increase; the population is aging, ever more people are living with a long term health condition and cancer now affects 50% of people.
More accurate diagnosis
Of course, one reason why more cases of Legionnaires’ disease are being identified could partly be a case of better, more accurate diagnosis. While it is simple to diagnose with a urine test, all too often Legionnaires’ disease is mistaken for pneumonia as the symptoms are very similar. It’s long been believed that Legionnaires’ disease is under-reported but perhaps these figures indicate a change of circumstances.
Increase in hospital-acquired infection
While the numbers remain small (14 cases out of 388), the proportion of people catching Legionnaires’ disease while in hospital (denoted as nosocomial in the statistics) more than doubled on the previous year. Whether this is due to the well-documented challenges currently faced by the NHS or part of the general upward trend in hospital-acquired infections, it’s not clear.
Whatever the reasons for the rise in the number of cases, it is nonetheless true that Legionnaires’ disease is largely preventable, which is no doubt precisely why the Government has chosen to publicise the problem more widely.
While the leaflet is primarily focused on informing householders of the process used for water sampling and testing for Legionella once an infection occurs, it also sets out in simple terms how and why Legionella can become a problem in the first place.
Since prevention is always better than cure, we’d advocate taking a proactive approach to ensuring that Legionella doesn’t get a foothold in your domestic water system. Our blog is jam-packed with advice on how to do this so we won’t repeat it here, but rest assured that there are several simple and effective measures for controlling the risk of Legionella in your home or rental property and it’s never too late to implement them.