Although we may not realize it, we are surrounded by millions of microorganisms throughout our lives. Everywhere. This should not alarm us: most of them are completely harmless.

However, there is a small group of them that under certain conditions can pose a serious threat to our health. Among them is Legionella, a bacterium that proliferates in water tanks in close proximity to humans, such as large cooling systems.

Legionella or legionellosis is a disease caused by the bacterium Legionella pneumophila, which basically presents two completely different clinical forms: on the one hand, pulmonary infection or Legionnaires’ disease, characterized by pneumonia with high fever, and the form known as Pontiac fever, which manifests itself as an acute febrile syndrome. Thus, as regards the severity of the disease, it can range from a mild cough to severe pneumonia leading to death caused by progressive lack of air in the lungs, shock and multi-organ failure.

What is Legionella?

Legionella is the common name for the bacterial genus Legionella. They inhabit stagnant water at a certain temperature (preferably above 35 degrees), such as those sometimes found in the water systems of large buildings (offices, hotels, hospitals, housing communities), in humidifiers, in spray machines, in irrigation systems or in hot springs. Fortunately, proper hygiene and prevention can prevent their proliferation.

Some (but not all) Legionella species can infect humans, causing respiratory symptoms that can vary in severity from mild to severe and potentially life-threatening. The most common route of infection is through inhalation of small droplets of contaminated water, which explains why it often occurs in large outbreaks with the same source of the pathogen.

What are its symptoms of Legionella?

Legionella produces two pictures of different severity, depending on factors such as the amount of bacterial matter that enters the organism and the characteristics of the patient.

The milder form is known as Pontiac fever, with a flu-like course and characterized by symptoms such as fever, headache, muscle pain, fatigue and general malaise. This form of the disease usually disappears on its own.

In contrast, Legionnaires’ disease, a form of pneumonia, is considerably more serious. Its basic symptomatology consists of high fever, cough and shortness of breath (dyspnea). It is often more severe than other more common forms of pneumonia, and may cause additional symptoms such as abdominal pain and diarrhea.

In the most extreme instances, Legionella can cause complications such as respiratory failure, septic shock and acute renal failure.

How is Legionella treated?

The main line of treatment against Legionella is, as with the vast majority of pathogenic bacteria, the use of antibiotics. Naturally, however, Legionnaires’ disease does not always respond well to this strategy.

In severe cases, hospitalization with patient support, such as fluid replacement or respiratory support, may be necessary.

Prevention is therefore essential, and many countries have strict regulations in place on the maintenance of systems that include bodies of water and that present a risk of spreading the bacteria.

On the other hand, it has been shown that smokers are at greater risk of contracting the disease and of developing severe symptoms, so to minimize the risks it is recommended to avoid smoking.


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