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Legionnaires disease- Frequently Asked Questions

Legionnaires' disease is a severe form of pneumonia caused by the Legionella bacterium, most commonly Legionella pneumophila. It was named after an outbreak in 1976 when many people who attended an American Legion convention in Philadelphia became ill.

Is Legionnaires' disease contagious?

No, Legionnaires' disease is not contagious and cannot be transmitted from person to person. It is acquired by inhaling aerosolised water droplets containing Legionella bacteria from contaminated environmental sources.

What should I do if I suspect I have Legionnaires' disease?

If you develop symptoms of Legionnaires' disease, especially if you are in a high-risk group or have been exposed to potential sources of Legionella contamination, seek medical attention promptly. Early diagnosis and treatment can greatly improve outcomes.

How to control the risks of legionella in my water systems?

An integral part of preventing or adequately controlling legionella bacteria is the maintence and design of your water services.

It is important to put in place appropriate controls and introduce a course of action to prevent any risks from legionella.

To do so you should:

·        Develop a schematic diagram.

·        Identify the responsible person to carry out or source the reputable company to manage the risk assessment.

·        Examine current control methods and precautions.

·        Avoid water temperatures and conditions that favor the growth of legionella and other microorganisms.

·        Ensure water cannot stagnate in the systems by removing redundant pipe work.

·        Keep the system and the water in it clean.


Who can undertake a Legionella risk assessment?

The responsible person or person in control of premises is responsible for helping manage your health and safety duties, e.g take responsibility for managing risks. As an employer you have a duty to safeguard your employees.

If you decide to hire contractors to carry out a risk assessment, it is still the responsibility of the person in control of the premises to ensure that the work is carried out to the required standards.

Is a Legionella Risk assessment required if I am not storing hot or cold water in my system?

A legionella risk assessment is still required as there are many other factors such as dead legs, showerheads, and/or long runs of pipe work containing warm water. A legionella risk assessment should also be considered if there are high risk individuals at the premises, for example in hospitals and Care homes.

How do I test or monitor legionella from my water system?

Water system – sampling should be carried out in accordance with BS7592. Water samples should be tested by a UKAS-accredited laboratory that takes part in a water microbiology proficiency testing scheme.

How often should I test for Legionella?

The frequency of testing will depend on the system that you have in place and the outcome of your legionella risk assessment. For open systems such as cooling towers and spa pools, routine testing should be carried out at least quarterly.

Enclosed systems such as hot and cold-water systems, testing is subject to the circumstances within that building, for example if the recommended temperatures or disinfection concentrations are not being consistently achieved then testing would be required.

What is the business impact of Legionnaires Disease?

  1. Financial Costs:

  • Dealing with a Legionnaires' disease outbreak can incur substantial financial costs for businesses. These may include medical expenses for affected individuals, legal fees, compensation claims, and potential fines.

  • Temporary closure of facilities for disinfection and remediation measures can result in lost revenue and productivity, as well as damage to customer relationships.

  1. Reputation and Brand Image:

  • Public perception of a business can be significantly impacted by a Legionnaires' disease outbreak. Negative publicity surrounding a health crisis can tarnish a company's reputation and erode customer trust.

  • Businesses that fail to demonstrate proactive measures for preventing Legionella contamination may be viewed as negligent, leading to long-term damage to their brand image.

  • Implementing robust risk management strategies and business continuity plans is essential for minimising the impact of Legionnaires' disease on business operations.

  • Proactive measures such as regular maintenance of water systems, monitoring for Legionella bacteria, and employee training on preventive measures can help mitigate the risk of outbreaks.

Legionnaires' disease presents not only a health risk but also significant implications for businesses, including legal, financial, reputational, and operational impacts. By prioritising preventive measures, compliance with regulations, and proactive risk management, businesses can protect their employees, customers, and bottom line from the adverse effects of Legionella contamination.









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