Legionnaires' disease: symptoms, causes, is it contagious and treatment

The NHS lists a cough, shortness of breath, chest pain or discomfort (particularly when breathing or coughing), a high temperature and flu-like symptoms. The HSE says the initial symptoms are similar to flu: high temperature, feverishness and chills, cough, muscle pains and headache, and it can lead on to pneumonia, diarrhoea and signs of mental confusion.

Because it looks like other illnesses, it can be hard to spot. An NHS Highland clinical guideline notes that the pneumonia can present in atypical ways, with diarrhoea and gastrointestinal symptoms, confusion, low sodium (hyponatraemia), abnormal liver function tests and a non-productive cough or small amount of sputum.

The HSE says a urine or blood test will help in deciding whether an illness is Legionnaires' disease. The UK Health Security Agency describes it as a severe pneumonia caused by the legionella bacterium, and says it can cause long-term health problems.

Legionnaires' disease is a form of pneumonia caused by legionella bacteria. The HSE calls it a potentially fatal form of pneumonia and says everyone is susceptible, with the risk increasing with age. People at higher risk include those over 45, smokers and heavy drinkers, people with chronic respiratory or kidney disease, diabetes, lung and heart disease, and anyone with an impaired immune system.

The HSE says legionellosis is the collective term for diseases caused by legionella, including the most serious Legionnaires' disease and the similar but less serious Pontiac fever and Lochgoilhead fever. Legionnaires' disease is a notifiable disease in England and Wales, so health professionals must inform local health protection teams of suspected cases.

You can get Legionnaires' disease if you breathe in tiny droplets of water containing the bacteria. The NHS lists air conditioning systems, humidifiers, spa pools and hot tubs, and taps and showers that are not used often as possible sources. It is usually caught in hotels, hospitals or offices, and is less common at home.

The HSE says legionella bacteria are widespread in natural water systems such as rivers and ponds, but the conditions are rarely right for people to catch the disease from these sources. Outbreaks occur from exposure to legionella growing in purpose-built systems where water is kept at a temperature that encourages growth, such as cooling towers, hot and cold water systems and spa pools. Growth is favoured when water is between 20 and 45 degrees C, droplets can form, water is stored or recirculated, and deposits like rust, sludge or scale provide nutrients.

The HSE adds that cases are often caught in the UK, but a number occur abroad.

No, not in the usual sense. The HSE says Legionnaires' disease is not known to spread from person to person. The NHS says you cannot usually get it from other people with the infection, from drinking water that contains the bacteria, or from places like ponds, lakes and rivers.

This is why public health teams focus on finding the water source, which the HSE says employers and those in control of premises must assess and manage.

The NHS says you may need to go into hospital. Treatment may include antibiotics given directly into a vein, oxygen through a face mask or tubes in the nose, and a machine to help you breathe. When you start to get better you might be able to take antibiotic tablets at home, and antibiotic treatment usually lasts 1 to 3 weeks.

The HSE says the illness is treated with an antibiotic called erythromycin or a similar antibiotic. NHS Highland guidance for clinicians says legionella is covered by macrolides and quinolones, that a positive urine antigen test confirms it but a negative result does not exclude it, and that if suspicion is high doctors treat with antibiotics empirically.

The NHS says most people make a full recovery, but it might take a few weeks to feel back to normal. The World Health Organization notes that Legionnaires' disease always requires antibiotic treatment after diagnosis and that recovery is usually complete after several weeks or months.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have symptoms of Legionnaires' disease such as a cough that has lasted 3 weeks or more, coughing up blood, chest pain that comes and goes or happens when breathing or coughing, or feeling short of breath. Tell them where you have been in the last 10 days, such as if you stayed in a hotel, spa or hospital.

The HSE says that if you develop flu-like symptoms and worry it might be Legionnaires' disease, you should see a doctor, and if you suspect your illness is a consequence of your work you should tell your manager, health and safety representative and occupational health department.

The HSE says employers and those in control of premises must assess and manage the risk of legionella in water systems, including landlords, who have responsibilities to keep tenants safe. The NHS names taps and showers that are not used often as a possible source.

The HSE notes the risk increases where water is between 20 and 45 degrees C, is stored or recirculated, and deposits such as rust, sludge or scale are present, which is why premises are expected to assess and control those conditions.

Suspected Legionnaires' disease is assessed through an urgent GP appointment, NHS 111 or hospital care, and is a notifiable disease. Private hospitals can provide the same antibiotic treatment, but severe pneumonia needs hospital-level care.