What Is Legionnaires' Disease? What Causes Legionnaires' Disease?

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Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Respiratory / Asthma;  Water - Air Quality / Agriculture
Article Date: 12 Sep 2010 - 7:00 PDT

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With the current outbreak of Legionnaires' disease in south Wales, here are some facts about the illness.

Legionnaires' disease, also called Legionellosis is a lung infection, a form of pneumonia which can be fatal, caused by the legionella bacterium. The name Legionnaires' disease emerged in 1976 - in July there was an outbreak of pneumonia among delegates at a convention of the American Legion in Philadelphia. In January of the following year, the causative agent was identified as a previously unknown bacterium, which was subsequently named Legionella.

Most cases of Legionnaires' disease occur as single isolated cases, not linked to any recognized outbreak, despite the infection's significant media attention. If outbreaks do occur, they tend to do so in the summer or early autumn; but they may occur at any time of year.

Legionella bacteria commonly exist in rivers and lakes, and some other water sources, generally in low numbers. Occasionally, they may get into artificial water supply systems, as may be the case with evaporative condensers associated with air conditioning and industrial cooling or anywhere where artificial water is being supplied or used.

People catch legionnaires' disease by inhaling small droplets of tainted water, but an infected person cannot pass the infection onto somebody else - you cannot catch legionnaires' disease from other infected people.

Legionnaires' disease is more likely to occur in places which have complex water supply systems, such as hospitals, hotels, and buildings which cater for large numbers of people.

If the water is kept below 20C (68F) or above 60C (140F), Legionnaires ' disease outbreaks can be prevented.

Incidence of Legionnaires' Disease

According to the National Health Service (NHS), UK, there were 551 reported cases of Legionnaires' disease in England and Wales in 2006, of which 160 were probably infected while travelling overseas. Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S.

As Legionnaires' disease signs and symptoms are often mild, it is likely that the real number of infections is considerably higher than the reported ones.

What are the signs and symptoms of Legionnaires' Disease

Legionnaires' disease may be hard to diagnose at first because its signs and symptoms may be very similar to other forms of pneumonia.

Signs and symptoms usually appear between 3 to 6 days after initial infection; more rarely it may be just 2 days or up to 10 days. Signs and symptoms of Legionnaires' disease typically include:

• a high fever
• chills
• a cough
• muscle aches
• headaches

In some cases there may be an initial stage during which the patient experiences just muscle aches and a mild headache, before the other signs start to appear a couple of days later. When more severe symptoms appear, the fever will be high, about 40C (104F), or even higher. The muscle pains often get worse, and the patient starts to have chills.

If the bacteria get into the patient's lungs, which often occurs, there may be a persistent cough, shortness of breath and chest pains. The cough may be dry at first, but can eventually have a lot of mucus and even blood as the infection develops.

Approximately one third of infected patients will also experience nausea, vomiting and diarrhea. Those with gastrointestinal symptoms will usually have an extremely reduced appetite.

According to the National Health Service (NHS), UK, approximately 50% of patients with legionnaires' disease will experience confusion and alterations to their mental state.

What are the causes of Legionnaires' Disease

The bacteria which cause Legionnaires' disease - Legionella - exist in rivers, lakes and other places with fresh water - usually in low numbers because the water temperature in such places is too low for the bacteria to multiply rapidly.

Artificial water systems on the other hand, where water temperatures may be higher - between 20-45C (68-113F) - are sometimes ideal environments where the bacterium can multiply rapidly and spread, infecting major parts of the water system.

For the bacteria to reproduce and spread rapidly it needs the right temperature and the right food. Impurities, such as algae, sludge, rust and lime scale are types of food for this sort of bacteria.

So, any hotel, hospital or large building with an air conditioning system that uses water for cooling might sometimes have the ideal environment in which the bacteria can thrive.

Experts say that any type of artificial water system can potentially become contaminated, including fountains, baths, showers, water taps, gardening sprinklers, spas and humidifiers used to display food.

Risk factors - The following people have a higher risk of developing Legionnaires' disease: smokers, people aged over 50 years, individuals with kidney disease, cancer patients (especially lung cancer or leukemia), people with diabetes, and patients with certain lung condition, such as COPD (chronic obstructive pulmonary disease).

How is Legionnaires' Disease diagnosed?

Legionnaires' disease is not easy to diagnose if the doctor does not have the right information. The National Health Service (NHS), UK, advises patients to tell their doctor if they have been in a large building for some time, such as a hospital or hotel. As one third of Legionnaires' disease cases in the UK are contracted abroad, people who have been travelling overseas should tell their doctor.

Urine test - this will detect antigens, special proteins produced by the immune system to fight the Legionella bacteria.

Blood tests and an imaging scan of the chest, such as an X-ray may be ordered to check the state of the patient's kidneys and lungs.

If the doctor wants to determine whether the infection has got into the brain, a lumbar puncture (spinal tap) may be ordered - a small sample of CSF (cerebrospinal fluid) is taken from the base of the spine.

What are the treatment options for Legionnaires' Disease?

Treatment typically involves a 10 to 14 day course of intravenous (injected) antibiotics. The medication may cause nausea, dizziness, headaches, loss of appetite, and chest pains.

In some cases intravenous fluids may be administered to prevent dehydration.

Patients with weak immune systems or chronic conditions, such as diabetes, as well as very elderly individuals will be hospitalized.

With serious lung infections the patient will be given oxygen.

What are the possible complications of Legionnaires' Disease?

Respiratory failure - the body does not get enough oxygen from the lungs to function properly.

Kidney failure - there can be a serious build-up of fluids and waste in the blood

Septic shock - blood pressure can suddenly drop dramatically, reducing the blood supply to vital organs, including the brain and kidneys. This is caused by blood infection.

In the UK, approximately 10% of all patients with Legionnaires' disease die from a serious complication.

Preventing Legionnaires' Disease?

Proper maintenance of water systems is vital to prevent Legionnaires' disease outbreaks. The water must be kept below 20C (68F) or above 60C (140F). Impurities should not be allowed to build up in the water.

Sources: National Health Service (NHS), UK, Centers for Disease Control and Prevention (CDC), USA.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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