Legionella bacteria naturally occur in many water sources such as ponds, lakes, and rivers. However, they can also be present in manmade water systems, such as those found in buildings and equipment.
That said, sampling for legionella is a practical and sensible way to monitor how safe the water in your building is. Sampling can act as confirmation that a water safety plan and associated control methods are working as they should be.
Given the nature of Legionella, it’s almost certain that it will be present in any body of water. Usually, there’s nothing to worry about, providing the count is relatively small, but when a sample result comes back possible, it’s all too easy to panic.
In this blog, we discuss what you need to do if you discover legionella in your water systems.
The presence of a confirmed positive Legionella count strikes fears in all those who have an involvement with water safety. The first you need to do after discovering you have legionella on-site is not panic!
A positive test result for the bacteria isn’t necessarily a sign of non-compliance with health and safety guidelines. Indeed, legionella bacteria is present in almost all natural water sources, and it is only certain conditions in man-made water systems that can encourage growth and lead to risk.
These conditions will have been identified in your legionella risk assessment, which is also where you would have identified the need for water testing.
Your priority following a positive test result for legionella bacteria on-site should be to investigate and resolve the root cause in the immediate and longer terms.
In the lab, a water sample can show three broad groups of Legionella bacteria. The first two groups show different types of Legionella pneumophila. The final group covers several dozen other types of Legionella species.
- Legionella pneumophila — serogroup 1: This is the strain of bacteria most commonly associated with cases of Legionnaires’ Disease
- Legionella pneumophila — serogroup 2-14: A little safer than serogroup 1, usually associated with non-fatal illnesses like Pontiac Fever
- Legionella Species: This primarily covers over 40 species of Legionella that are commonly found in a wide spectrum of water, both artificial and natural. While not as big of a concern as the serogroups, their presence can indicate that conditions within the system could support the growth of the bacteria.
Results are usually shown as cfu/l which is the number of colony-forming units per litre of water. An exact count is often not provided or necessary as once a threshold has been reached, the exact numbers will make little difference.
Not detected/<100 cfu/l – Not detected doesn’t necessarily mean not present or that there are no risks within the system.
>100 – <1000 cfu/l – A low-level detection that is likely to require more context in order to effectively proceed. If multiple samples have been taken and the majority of them have returned positive, the system is most likely colonised albeit at a low level. Should the minority return positive, this will warrant a resample and the outcome of that will determine the best action to take.
>1000 cfu/l – Should any sample return with a level this high, immediate action is required to prevent cases of Legionnaires’ Disease from arising. This includes taking the system/outlets out of use and carrying out a thorough clean and disinfection of the system.
By themselves, any of these can be a cause for some concern and action, but it’s the combination of the Legionella species and the amount found that will determine how to proceed.
Follow Written Scheme of Control
The approach in dealing with any positive Legionella sample results (either as a result of a defined sampling strategy or in response to a particular issue) should be defined clearly within the Written Scheme.
This will provide a prescriptive process, that is easily understood by those persons involved at the operational level who are responsible for investigating and resolving the issue.
Simply put, the response to a positive result should have been agreed upon and documented before any sampling programme – whether undertaken in-house or by contractors.
To establish a root cause of the positive count, the prescriptive process for the protocol must include a systematic elimination of potential issues, including the sampling process itself i.e. has the process been compromised causing the positive count, as such a competency review of those who’ve taken the sample, handling, transportation and accreditation of the lab.
Receiving a positive count result, appropriate measures must be undertaken to protect the occupants of the building where the samples were taken.
Things like location, the frequency of use, the chance of exposure and previous sample results all influence the measures needed to correct the matter.
For instance, it could be that all samples are fine except for one taken from a disused shower head. In that case, thoroughly cleaning it and flushing through that portion of the system is the best thing to do – ahead of another test, of course.
If raised levels are seen throughout the system, or the levels are high enough to be of real concern, the affected parts of the water system should be isolated and not used until measures are taken to reduce the bacterial growth.
In extreme cases, the entire water system may be shut down while this takes place. There have been lots of cases where buildings have been shut down until the situation is brought under control. Thorough disinfection and flush through of the entire system, along with intensive cleaning and maintenance where required, is often the only solution in this case.
Written scheme of control and legionella risk assessment must also be reviewed, including looking at ways of improving the design of your water system in order to remove any areas that the bacteria will be able to grow in.
Notify Relevant Stakeholders
Legionellosis is a statutorily notifiable disease in Ireland as defined by the Infectious Disease Regulations 1981 (S.I. No. 390 of 1981).
Under the Infectious Diseases (Amendment) (No. 3) Regulations 2003 (S.I. No. 707 of 2003), laboratory and clinical notification of legionellosis is mandatory. Cases should be notified to the MOH in the relevant department of public health.
Failure to do so could invite legal action and financial penalties.
Update the Records
It is essential to document all findings of the risk assessment, sampling and remedial actions undertaken. This not only ensures an adequate paper trail for auditors to know that the issue has been satisfactorily, it also helps new staff see what’s been done previously and what they need to continue to do to ensure future legionella compliance.
Records should be kept for the duration of the time for which they remain current and for at least two years after that. However, records detailing the monitoring inspections, tests and dates need to be kept for at least five years.
Get the Expert Guidance
Positive legionella test results can be extremely worrying for duty holders and people responsible for water safety.
In such situations, it is best to seek guidance from experts such as Celtic Water Solutions. Based on the data available and test results, our experienced consultants recommend a solution to ensure the building occupants are safe and your business is compliant with health & safety laws.
If you require any further information on our water hygiene and safety solutions, feel free to consult with our team of experts.
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