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Who is most at risk?
Legionnaires’ disease can affect anyone, but some people are much more likely to become seriously ill if they are exposed to the Legionella bacteria. The greatest risk is usually for older adults, especially people over 50. Men are also diagnosed more often than women, although anyone can get the infection.
People are more vulnerable when their immune system is weaker or when they already have another health condition. In these cases, the body may struggle to fight off the infection effectively. That is why certain groups in the UK are advised to take extra care around water systems where Legionella can grow.
Age and existing health conditions
Older people are at higher risk because the body’s natural defences often become less effective with age. This does not mean younger adults are safe, but they are less likely to develop severe disease. The risk rises further if someone is frail or has multiple long-term conditions.
People with chronic illnesses such as lung disease, kidney disease, diabetes, heart disease, or cancer may also be more at risk. These conditions can make it harder to recover from a severe chest infection. Someone who is already unwell may also be more likely to need hospital treatment.
Weakened immune system
Anyone whose immune system is suppressed has a greater chance of developing Legionnaires’ disease. This includes people having chemotherapy, people taking steroid treatment for a long time, and those living with conditions that affect immunity. Organ transplant recipients may also be at higher risk because they take medicines to stop rejection.
In these situations, even a relatively small exposure to Legionella can lead to serious illness. Symptoms may also develop quickly or become severe before the person realises they have been exposed. Prompt medical attention is especially important for these groups.
Smoking and lifestyle factors
Smoking is an important risk factor for Legionnaires’ disease. It damages the lungs and makes it harder for the body to clear infections from the airways. People who smoke or who have a history of smoking may therefore be more likely to become ill after exposure.
Heavy alcohol use may also increase risk, partly because it can weaken general health and make it easier to aspirate contaminated water. Poor overall health, recent surgery, or long periods of bed rest can also make a person more susceptible. The risk is often greater when several of these factors are present together.
People exposed to higher-risk settings
Legionella grows in warm water systems, so people are more at risk if they use poorly maintained showers, hot tubs, cooling systems, or stored water systems. This matters in homes, care settings, hotels, hospitals, and workplaces. Outbreaks can happen when water systems are not properly managed.
In the UK, prevention is especially important in buildings with complex plumbing or large water systems. Most healthy people will not become ill from everyday water use, but vulnerable groups should be more cautious if they are in a known risk setting. If someone at higher risk develops a cough, fever, or breathlessness after possible exposure, they should seek medical advice quickly.
Frequently Asked Questions
The main Legionnaires' Disease risk factors include older age, smoking, chronic lung disease, weakened immune system, recent surgery, cancer, kidney disease, diabetes, and exposure to contaminated water systems such as cooling towers, hot tubs, showers, and large building plumbing systems.
People age 50 and older are at higher risk for Legionnaires' Disease risk factors because immune defenses tend to decline with age, making infection more likely after exposure to Legionella bacteria.
Smoking is a major Legionnaires' Disease risk factor because it can damage the lungs and reduce the body's ability to clear bacteria from the respiratory tract, increasing the chance of infection.
Chronic lung conditions such as COPD, emphysema, and other long-term respiratory diseases increase Legionnaires' Disease risk factors by making it harder for the lungs to fight off infection.
A weakened immune system increases Legionnaires' Disease risk factors because the body is less able to control Legionella bacteria. This can happen due to immune-suppressing medications, organ transplants, HIV, or certain medical treatments.
Cancer and cancer treatments can increase Legionnaires' Disease risk factors by weakening immune defenses, especially during chemotherapy, radiation, or other treatments that lower white blood cell counts.
Recent hospitalization or surgery can increase Legionnaires' Disease risk factors because exposure to contaminated water systems in healthcare settings may occur, and recovery can temporarily weaken the body's defenses.
Diabetes is a Legionnaires' Disease risk factor because high blood sugar can impair immune function and increase susceptibility to infections, including those caused by Legionella bacteria.
Yes, kidney disease and dialysis can increase Legionnaires' Disease risk factors because chronic illness and repeated medical care may weaken the immune system and increase exposure risk.
Travel and hotel stays can be Legionnaires' Disease risk factors if water systems are contaminated, especially in large buildings with complex plumbing, decorative fountains, spas, or poorly maintained hot tubs.
Hot tubs and spas can contribute to Legionnaires' Disease risk factors when they are not properly cleaned and disinfected, allowing Legionella to grow and spread in warm aerosolized water.
Cooling towers are included among Legionnaires' Disease risk factors because they can release contaminated water droplets into the air if they are not properly maintained and disinfected.
Men are diagnosed with Legionnaires' disease more often than women, so male sex is considered a demographic factor associated with increased Legionnaires' Disease risk factors, though the reasons are not fully understood.
Heavy alcohol use can increase Legionnaires' Disease risk factors by weakening the immune system, affecting lung defenses, and raising the chance of aspiration or poor overall health.
Yes, organ transplant recipients are at higher risk because anti-rejection medicines suppress the immune system, making Legionnaires' Disease risk factors more significant for this group.
Yes, contaminated showers and faucets can be Legionnaires' Disease risk factors because Legionella bacteria can spread in tiny water droplets when infected plumbing systems are used.
Long-term care facilities can increase Legionnaires' Disease risk factors if their water systems are not properly monitored and disinfected, especially for residents who are older or medically fragile.
Age and smoking together can significantly raise Legionnaires' Disease risk factors because aging weakens immune responses and smoking damages the lungs, creating a higher chance of infection after exposure.
Warm, stagnant, or poorly disinfected water conditions are most associated with Legionnaires' Disease risk factors because Legionella bacteria grow best in these environments and can spread through aerosolized droplets.
Yes, Legionnaires' Disease risk factors can be reduced by avoiding contaminated water sources when possible, quitting smoking, managing chronic illnesses, and ensuring that buildings and water systems are properly maintained and disinfected.
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