and Pontiac Fever
If you would like to know more about Legionnaires Disease symptoms and diagnosis, and about Legionnaires Disease treatments, read the following article for more information.
Legionnaires disease causes a serious pneumonia (lung infection). You get the infection by breathing in droplets of water which contain legionella bacteria. The earlier the illness is treated with antibiotics, the better the likely outcome. The illness is fatal in some cases. Pontiac fever is a milder illness caused by the same bacteria.
What are legionnaires disease and pontiac fever?
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 bacteria which 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. Piped water, especially hot water, in large buildings with long runs of pipework can be a source of the bacteria. Other sources include:
- Circulating water droplets in air-conditioning and cooling systems.
- Whirlpool spas and other warm-water baths.
- Decorative fountains.
- Cooling towers.
- Nebulizers and humidifiers if topped up with contaminated tap water.
- Potting compost was the source of several outbreaks in Australia.
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. If just one person in an area 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 immunity to infection with such things as alcohol dependence, AIDS, 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. 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 2-10 days. That is, symptoms start 2-10 days after first being infected.
- Typical first symptoms are: cough, fever, 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'. A sharp pain in the side of the chest may develop if the infection involves the pleura. (This is the membrane between the lung and the chest wall.)
- Common 'non-lung' symptoms include confusion and diarrhoea.
- Complications develop in some cases and can cause heart, brain or kidney problems.
Legionnaires Disease
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 bacteria or other germ that is causing the pneumonia. In addition, if legionnaires disease is suspected, a urine test is the easiest and quickest test to confirm that the germ causing the illness is the legionella bacterium. (The urine test detects certain antigens - proteins from the legionella bacteria that get into the bloodstream and are passed out in the urine.)
What is the treatment for legionnaires disease?
- You will normally be admitted to hospital.
- Antibiotics are started as soon as possible. The most commonly used antibiotic to treat legionnaires disease is erythromycin. Sometimes other antibiotics are used.
- 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) of legionnaires disease?
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 high 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.
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. No treatment is needed other than paracetamol or ibuprofen to ease a 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 bacteria.
At present there is no vaccine that can protect against legionella bacteria.
©EMIS and PIP 2005 Updated: November 2005
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