What You Need to Know About Legionnaires’ Disease
Understanding what Legionnaires’ disease is
Legionnaires’ disease is a type of lung infection (pneumonia) caused by Legionella bacteria. These bacteria thrive in warm water environments such as cooling towers, air-conditioning systems, spa pools, and sometimes poorly maintained water systems. People usually become unwell after breathing in tiny droplets of contaminated water. It is not spread from person to person.
Who is more at risk
While anyone can develop Legionnaires’ disease, some people have a higher risk of becoming seriously unwell. This includes older adults, people with chronic lung disease, heart disease, diabetes, weakened immune systems, or those who smoke. People exposed to contaminated water systems in workplaces, hospitals, hotels, or industrial environments may also be at higher risk.
What symptoms to look out for
Symptoms often develop a few days after exposure and usually begin like a flu-like illness. Common features include fever, chills, headache, tiredness, muscle aches, and a persistent cough. Some people experience chest pain, shortness of breath, confusion, nausea, vomiting, or diarrhoea. Because symptoms overlap with other respiratory illnesses, medical assessment is important if pneumonia is suspected.
Why early diagnosis matters
Legionnaires’ disease can become serious if not treated promptly. Diagnosis is usually made through medical assessment, chest imaging, and specific laboratory tests. Early treatment with appropriate antibiotics reduces complications, speeds recovery, and improves outcomes. If you have pneumonia-like symptoms and risk factors for Legionella, your GP or hospital team will arrange appropriate investigation.
Treatment and recovery
Most people diagnosed early respond well to treatment. Recovery time varies depending on overall health and illness severity. Some people may need hospital care, especially if breathing is affected or other health conditions are present. Rest, hydration, good follow-up care, and monitoring are important parts of recovery.
Prevention and reducing risk
Legionnaires’ disease is strongly linked to environmental conditions rather than personal behaviour. Good maintenance of water systems, regular cleaning of cooling towers, safe spa and pool management, and proper temperature control of water systems reduce risk at a community level. At an individual level, reducing smoking, maintaining lung health, and seeking care early for respiratory illness help protect health.
When to seek medical help
Seek prompt medical review if you experience persistent high fever, cough, breathing difficulty, chest pain, confusion, or signs of pneumonia — especially if you have risk factors or recent exposure to air-conditioning systems, spa pools, or large building water systems. Early care genuinely makes a difference.
If you are unsure about symptoms or your risk, your GP can help assess, explain testing, coordinate care, and support your recovery and wellbeing.
This article provides general health information only and does not replace medical advice. Please speak with your GP for personalised care.