Legionnaires' Disease

What are legionnaires' disease and pontiac fever?

Legionnaires' disease (also called legionellosis) is an uncommon infection caused by a bacterium (germ) called legionella. There are two types of illness which can develop after being infected with this bacterium:

• Legionnaires' disease. This causes a pneumonia (lung infection). It is usually a severe illness, sometimes fatal.
• Pontiac fever. This is when the bacteria cause a flu-like illness. It is not usually serious.

Some background about Legionella bacteria

In 1976 an outbreak of pneumonia occurred among American legionnaires (ex-servicemen) who attended a conference. 221 people developed pneumonia, and 34 died. A bacterium (germ) that had never been identified before was found to be the cause and was named 'Legionella pneumophila' (pneumophila means 'lung loving').

Since then, many different types of bacteria in the 'Legionella' species have been identified. Legionella bacteria live in fresh water and mud and are found all over the world. Most cases of illness are caused by Legionella pneumophila, the type first identified.

How do you get legionnaires' disease or pontiac fever?

Outbreaks that affect many people occur from time to time

The source of the bacteria in an outbreak is usually a man-made water distribution system where the bacteria have multiplied in great numbers. For example, warm storage tanks where the water stagnates is ideal for Legionella bacteria to multiply greatly. This means that legionnaires' disease can be caught from:

• Piped water, especially hot water, in large buildings where long runs of pipework can be a source of the bacteria.
• Circulating water droplets in air-conditioning and cooling systems, cooling towers and evaporative condensers.
• Whirlpool spas ('Jacuzzis'), other warm-water baths and shower heads.
• Decorative fountains.
• Nebulizers and humidifiers (including some types of breathing equipment) if topped up with contaminated tap water.
• Potting compost.
• Plastics factories.

You become infected by breathing in water droplets (aerosol) that are contaminated by many Legionella bacteria. Therefore, an outbreak can affect many people in the same hospital, hotel, building, office complex, etc, around the same time.

Sporadic (individual) cases

Individual cases occur from time to time. Where only one person is infected, then the source of the bacteria is not usually found. About 2 in 100 cases of pneumonia that occur in previously well people are thought to be due to Legionella bacteria.

You are more likely to develop legionnaires' disease (and pneumonia caused by other bacteria) if you are already in poor health; if you have a chest disease; if you smoke; if you have low resistance to infection - due to illness such as alcohol dependence, AIDS, immune suppressing medication, long-term steroid medication, diabetes or other serious illnesses.

Note: person-to-person spread of Legionella bacteria does not occur. Therefore, you cannot catch legionnaires' disease from an affected person. Also, you cannot catch legionnaires' disease from drinking contaminated water. To get the illness you need to breathe in water droplets that contain Legionella bacteria.

What are the symptoms of legionnaires' disease?

• The incubation period is normally 2-10 days (but sometimes can be 14 days). That is, symptoms start 2-10 days after first being infected.
• Typical first symptoms are: cough, fever (high temperature), sweats, shivers, being off food, and feeling generally unwell. Headaches and aches and pains are common. The sputum may become yellow/green, and is sometimes bloodstained.
• Symptoms tend to become worse quite quickly as the infection spreads through the lung tissue. You may become breathless, breathe fast, and develop a 'tight chest'. You may have pain in the side of the chest when breathing ('pleuritic pain').
• Common 'non-lung' symptoms include confusion and diarrhoea.
• Complications develop in some cases and can cause heart, brain, kidney, gut or blood problems.

How is legionnaires' disease diagnosed?

A chest X-ray can confirm that you have pneumonia. However, pneumonia is common and there are many bacteria and other types of germs that can cause pneumonia. (Legionnaires' disease is an uncommon cause of pneumonia.)

Blood tests and sputum tests are then done to try and identify the bacterium or other germ that is causing the pneumonia. In addition, if legionnaires' disease is suspected, a urine test can confirm most (but not all) cases of Legionella infection.

What is the treatment for legionnaires' disease?

• You will normally be admitted to hospital.
• Antibiotics are started as soon as possible. The traditional antibiotic to treat legionnaires' disease (or suspected legionnaires' disease) is erythromycin. But other antibiotics are often used, for example: azithromycin, clarithromycin, levofloxacin, ciprofloxacin or doxycycline. If you are pregnant, erythromycin and azithromycin are safe for the baby. Sometimes a combination of antibiotics is used, if it is not yet certain whether the infection is due to Legionella or to other bacteria.
• Oxygen is commonly given.
• Intensive care with supportive treatments such as assisted ventilation may be needed if the pneumonia is severe.

What is the prognosis (outlook)?

Legionnaires' disease is a serious illness. If you were previously fit and well, you have about a 1 in 10 chance of dying from legionnaires' disease. If you were previously unwell, (for example, if you already have a lung disorder) then you have a higher risk of dying if you get legionnaires' disease. The outlook is best if the illness is diagnosed as early as possible, and you are treated with antibiotics as soon as possible.

After recovery from legionnaires' disease, you may get symptoms such as tiredness, poor concentration, cough or mild shortness of breath. These may take several months to clear up.

What are the symptoms and treatment of pontiac fever?

Pontiac fever is a milder illness caused by Legionella bacteria. It causes a flu-like illness which lasts just a few days. Symptoms include: fever, shivers, headache, muscle aches, tiredness and a dry cough. However, the infection does not affect the lung. Usually, no treatment is needed other than paracetamol or ibuprofen to ease fever and muscle aches.

It is not clear why some people get legionnaires' disease (with pneumonia) and some people get the milder pontiac fever when infected with Legionella bacteria. It is also thought that some people who are infected with Legionella bacteria do not become ill at all (a 'sub-clinical infection'.)

Can infection with Legionella bacteria be prevented?

As mentioned, the main cause of outbreaks of legionnaires' disease is from contaminated water sources. In the UK, and in many other countries, there are regulations on how to maintain water supplies and air conditioning systems used in large buildings. This keeps the number of Legionella bacteria very low to minimise the risk of infection. However, it is very difficult to completely eradicate this bacterium.

If you have a home humidifier or spa, follow the manufacturer's advice about maintenance and cleaning.

At present there is no vaccine that can protect against Legionella bacteria.