Legionella in Homes – When to Investigate Legionnaires’ Disease
This water safety article considers the risks associated with legionella in private homes, focusing on the role of local health regulators when investigating outbreaks of Legionnaires’ disease in the community.
The article looks at legionella risk levels in the home, current health and safety law, who decides if private households should be investigated, when to carry out water sampling, wider public health considerations and the importance of the risk assessment process.
What is legionella and where is it found?
Legionella bacteria live in natural water sources – ponds, rivers, and so on. However, they can also find their way into hot and cold water systems developed for use in all kinds of buildings. If bacteria levels reach certain thresholds, people who use those affected water systems could be exposed to the bacteria. This in turn can cause Legionnaires’ disease, a serious type of pneumonia that, while treatable with antibiotics, can occasionally lead to fatalities.
If Legionella bacteria are left to spread through a water system unchecked, it could lead to an outbreak that affects many people in the local area. This is rare but it can occur. Buildings most at risk are those with older or more complex water systems, such as cooling towers, especially if such water systems have dead legs or infrequently used sections of piping, taps, shower heads, or similar items.
Legionella in private homes
You’ll notice that we haven’t mentioned water systems in private homes. In the UK health and safety law is aimed at businesses and controlling risks in the workplace, not in private households. Additionally, private homes are generally thought to pose a low risk from Legionella bacteria in their water systems. It is unlikely that a home water system could be complex enough to pose a high risk. The water systems also tend to be used frequently, avoiding problems with stagnation. However, there are scenarios where certain households could be investigated for the risks caused by legionella contamination.
This is most likely to be considered when several clustered outbreaks of Legionnaires’ occur in a single area. If the discovered cases occurred in the community, any properties related to one or more people found to have contracted Legionnaires’ may be investigated. This would involve sampling the water to check for evidence of legionella.
It might also occur in cases where one or more people living in the property would be at greater risk of contracting Legionnaires’ disease and potentially suffering more severely if they did. This would include people aged 50 and over and those who have a suppressed immune system.
Another possibility may occur where several other sources have already been ruled out for an outbreak. There may be circumstances where those investigating the outbreak suspect there is good reason for a home to be the source of the bacteria
For example, if a property is left empty for a week or more, perhaps while the residents are on holiday, the water system should be flushed through upon return to the home. This is usually quite simple, turning on taps and shower heads safely (to avoid creating a spray) and letting them run for a while to flush through the system.
However, if this isn’t done, it could potentially mean raised levels of bacteria could affect those living in the household.
Who decides whether a home should be checked for legionella?
Two bodies would usually be involved in deciding if a household is investigated:
- The environmental health department of the relevant local authority
- The local health protection team (HPT)
If they considered one or more home environments to be of interest while investigating a local outbreak or cluster of cases, they may agree to sample the water systems in the affected households.
When to sample for legionella?
There are a number of conditions that need to be met before sampling for legionella in the home. Without checking these conditions first, unnecessary testing would be far more likely to occur.
Respiratory sampling from the affected individual(s) should be completed to determine whether Legionnaires’ disease is indeed present. Suspicion is not enough to warrant home testing.
Most cases of Legionnaires’ disease develop within two to 10 days after exposure to Legionella bacteria
Most cases of Legionnaires’ disease develop within two to 10 days following exposure to the bacteria. This window should be considered by those assessing the likelihood of the home as a possible source. If the timeline doesn’t line up with exposure to the home, testing in that environment would not be required.
It is also important to consider other circumstances present in the case. For example, there could be other sources for the Legionnaires’ infection. These sources could include those connected with travel, healthcare environments, the wider community, or a possible local outbreak.
The wider public health risk from Legionnaires’ should also be considered
Even where a single private household has resulted in a case of Legionnaires’ disease, the level of risk posed to the wider public could be low. Plenty depends on the nature of the household. For instance, a house would pose far lower risk levels than a private unit within a larger building that has one water system shared by everyone. This would increase the risk and therefore sampling of the water system would make more sense.
The importance of a legionella risk assessment
Finally, as with any commercial, industrial, or similar property, a legionella risk assessment of the water system in a household is required in this situation.
A legionella risk assessment will help investigators identify areas of concern
This approach allows investigators to understand whether any part of the system may pose a bigger risk than it should.
As mentioned earlier, a water system in a home that has been out of action for a week or more or that has outlets that are rarely used could be seen as a possible risk factor. Other recent issues with the water system could also point to a source of legionella.
Expert legionella risk management solutions
Legionella Control International is a world-leading legionella and water safety specialist. Our teams of experts support businesses and those responsible for the control of waterborne pathogens including Legionella bacteria in the workplace.
We will help you to protect your employees, customers and others in meeting your health and safety obligations in this specialist area.
We deliver a range of specialist risk management solutions including risk assessment, legionella testing, regulatory compliance auditing, training, expert witness support and other services that help keep people safe.
