Legionellosis - Legionnaire's Disease

The legionellosis, also known as disease (s) Legionnaire (s) is a potentially serious infection caused by a bacterium called Legionella pneumophila. The Legionnaire's disease is an infection not contagious, which is usually acquired through inhalation of contaminated water particles with the Legionella bacteria and can cause atypical pneumonia.

In this article we explain what is Legionnaire's disease, as is the transmission, what are its symptoms and what are the treatment options.

Various stages of disease
Various stages of disease

What is legionnaire's disease?

The Legionnaire's disease is an infection that was only recognized in 1976, following an outbreak of pneumonia among the participants of a convention of the American Legionnaire's, a group of US war veterans. The convention was held in a hotel in Philadelphia, whose central air conditioning system was contaminated by the bacterium Legionella pneumophila. Just a week after the convention, 130 participants of the event had been hospitalized and 25 had departed with a strange picture of chest pain, shortness of breath, cough and fever.

The origin of the disease was only recognized months later, after intensive research by the American health department. Both the disease, as its causative agent, science unknown until that moment, were baptized in honor of legionaries who became ill.

The discovery of Legionella pneumophila and its way of spreading caused a radical change in standards of hygiene and safety of air conditioning systems and water in general. However, despite care, dozens of new outbreaks of legionellosis continued in the world since the identification of the disease. There are cases even transmission within hospitals. The latest outbreaks have occurred in Portugal, Germany, Australia and the USA. The largest outbreak recorded to date occurred in Spain in 2001, with about 450 confirmed cases.

Since its identification, knowledge of Legionnaire's disease has increased considerably. We now know that Legionnaire's disease is transmitted by air, contaminated by water droplets, which can cause severe pneumonia, especially in the most infirm persons such as elderly or immunocompromised patients with pulmonary disease. The bacterium Legionella pneumophila can also cause a milder framework, called Pontiac's disease, which is very similar to the common cold.

Some bibliographical sources call legionellosis any infection by Legionella, including the milder forms. In this article we will refer to the severe form of the disease just as legionellosis or Legionnaire's disease. The mild form is always called Pontiac's disease. I will make this distinction to avoid confusion, since the Pontiac's disease is a benign form, which do not progress to pneumonia or risk of death.

Transmission forms of legionnaire's disease

As noted in the first paragraph of this article, legionellosis is not a contagious disease. There is no transmission from one person to another, so patients hospitalized with Legionnaire's not need to stay in isolation. If you have a relative or friend diagnosed with Legionnaire's disease, your concern should not be with the recent contact you had, but with the kind of environment in which both were recently present.

The transmission also seems to occur via water intake. You can not get Legionnaire's drinking water, but inhaling water contaminated particles in the air. We will explain in more detail.

The Legionella pneumophila is a bacterium that lives in aquatic environments, including lakes and streams. However, the natural sources of water, the amount of Legionella is very small, and the low risk of contamination. The bacterium seems like it is artificial water reservoirs. Places where water is stored, with mild temperatures (25 to 42°C), such as pipelines and reservoirs are ideal for the proliferation of Legionella. The presence of other aquatic organisms such as algae, amoebae, ciliates and other bacteria also help promote the growth of Legionella.

A multitude of water systems have been identified as potential sources of legionellosis. Among the most common are heating or cooling water, central air conditioners, hot tubs, showers, water high pressure equipment, humidifiers, fountains, fountains, sprays, steam saunas, etc. Any environment where there vaporization or emission of water particles can be a source of infection, where, logically, the water is contaminated with bacteria.

Just to illustrate, there are reported cases of Legionnaire's disease that were acquired because of fountain in luxurious lobby, whirlpool baths in spas and pools to clubs. Some cases of Legionnaire's disease acquired in hospitals occurred because the water pipe was colonized with the bacteria. There is also a case described in Italy contracted legionnaire's disease in a dental office, through contaminated water in high-pressure instruments that the dentist used to wash the mouths of patients during their procedures.

The use of copper pipe and chlorine in the presence of water greatly reduce the risk of colonization by Legionella pneumophila. Water systems of large establishments, including residential and commercial buildings, shopping malls, hospitals, clubs, hotels, etc., should undergo systematic quality controls of water from its reservoirs and pipelines. Outbreaks usually occur when there is negligence in controlling water quality in community settings. If the plumbing or the water tank of your building is contaminated, you can contract Legionnaire's to take a simple shower.

Despite the frightening picture that the above explanations can be painting, the fact is that Legionnaire's disease is a relatively uncommon disease, especially if we consider that billions of people worldwide are exposed daily to water aerosols. A recent study found that in Europe, legionellosis rate is approximately 10 cases per year for every 1 million people. In Brazil there are no clear epidemiological data, but if we extrapolate the existing rate in Europe, we arrive at an estimate of 2,000 cases per year.

It is also important to note that not everyone who is exposed to the bacterium Legionella pneumophila ends up developing a more severe form of disease. The infection rate is only 5%. Therefore, 95% of people exposed to the bacteria do not develop Legionnaire's disease. Within this 95% group, a lot of features Pontiac's disease, which has just passing unnoticed, like a common cold.

The Legionnaire's disease is uncommon in young and healthy people. The main risk factors for Legionnaire's disease is smoking and chronic obstructive pulmonary disease - COPD. Age over 55 years, excessive alcohol consumption, diabetes mellitus or immunosuppression (HIV, chemotherapy, use of corticosteroids...) are also factors that facilitate the emergence of the disease.

Symptoms of legionnaire's disease

Pneumonia is the most typical manifestation of Legionnaire's disease. The incubation period is on average from 2 to 10 days.

In early disease, the condition is usually mild, with dry cough, malaise, muscle pain and headache, similar to any common respiratory virus. From the second day, the picture begins to worsen. The cough becomes more intense and the sputum may be accompanied by blood. The framework involves a high fever, usually above 39°C, chest pain, shortness of breath and exhaustion. Gastrointestinal symptoms may also be present, including diarrhea, vomiting and abdominal pain.

Laboratory, the patient may have increased the number of leukocytes in the blood, changes in renal function, changes of the tests liver function and hyponatremia (low sodium levels in the blood). Blood in the urine is also common, but it usually microscopic, only detectable by urine test.

Patients with legionellosis must often be hospitalized and mortality rate varying from 5 to 30%.

Pontiac's disease

The Pontiac's disease, as already explained, is a much more benign infection. The bacteria that cause is the same, but the clinical picture is completely different.

Unlike Legionnaire's disease, Pontiac disease has a much shorter period of incubation, for 1 to 3 days. The clinical picture is of fever, malaise and headache. Productive cough does not usually occur and patients do not develop pneumonia. There is rarely need for hospitalization and infection heals spontaneously in 100% of cases.

Diagnosis of legionellosis

Rapid diagnosis of legionnaire's disease is essential, since the early initiation of appropriate treatment is clearly associated with improved outcome of the frame.

The level of suspicion should be high, since the Legionella pneumophila is usually not identified in tests normally done to diagnose common pneumonia.

For the diagnosis of legionellosis, two tests are often requested:
  • Research soluble antigens in the urine.
  • Culture of respiratory secretions.

Both tests mentioned above are not part of the initial research common pneumonia frames. So if the doctor does not think of legionellosis, it will not make the diagnosis early, as it will not ask the examinations necessary to do so.

Treatment of legionnaire's disease

The treatment of pneumonia caused by legionella should be done with antibiotics. As mentioned above, the earlier the antibiotic was started, the greater the chance of successful treatment. In mild cases, a patient may be treated with oral antibiotics at home. In more severe cases, hospitalization is necessary, and treatment with antibiotics is done intravenously.

The two most commonly used antibiotics for the treatment of Legionnaire's disease are levofloxacin or azithromycin. In both cases, the treatment is carried out for 7 to 10 days. In immunocompromised patients, or those with very serious condition, it can take 21 days of antibiotic therapy.

Patients with Pontiac disease, ie without the Legionella pneumonia, no need for hospitalization or antibiotics. Infection behaves like a common virus and cure themselves spontaneously after a few days without leaving any kind of sequel.

So far there is no vaccine against Legionella.

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