Legionellosis, the Disease Confirmed in Romania Too: Who Is at Risk of Severe Forms and What Symptoms Appear

Legionellosis is an infection caused by the Legionella bacterium, which primarily affects the lungs and can lead to a severe form of pneumonia. Infectious disease specialist Adrian Marinescu explained to Digi24.ro how the infection occurs, the signs that warrant medical attention, and which groups of people face a higher risk of complications.

How the disease spreads

The disease does not spread from person to person. Infection occurs almost exclusively through the inhalation of water aerosols contaminated with the Legionella bacterium.

The disease takes its name from an incident in the summer of 1976, when hundreds of veterans from the American Legion organisation attended a convention at a hotel in Philadelphia, USA. Many attendees developed severe pneumonia, and several people died. The epidemiological investigation revealed that the source was the hotel's air conditioning system, which had been contaminated with a bacterium unknown at the time. A year later, the pathogen was isolated and named Legionella pneumophila, and the disease became known as Legionnaires' disease, or legionellosis.

Confirmed cases in Romania

According to Dr Adrian Marinescu, Legionella infection exists in Romania, where cases have been confirmed — generally isolated, but with the potential for severe progression. A recent example is that of a Metrorex employee who was admitted to hospital and whose medical investigations confirmed a diagnosis of legionellosis. The National Institute of Public Health (INSP) has launched an epidemiological investigation to identify the source of contamination and to determine whether other individuals may have been exposed to the bacterium.

Sources of contamination

The most common sources are complex water installations and centralised air conditioning and cooling systems, used primarily in hotels, hospitals, office buildings, shopping centres, and other public spaces. Unlike domestic air conditioning units, these systems operate on water circuits and can promote the growth of the bacterium if they are not properly maintained and disinfected.

The bacterium thrives in stagnant or inadequately treated water, particularly at temperatures between 20 and 45 degrees Celsius — a range in which it multiplies rapidly. This is why the risk increases during warmer months, when high temperatures and intensive use of cooling systems encourage the proliferation and dispersal of the bacterium through aerosols. The danger does not come from brief contact with water, but from prolonged exposure to aerosols from contaminated sources.

Symptoms of infection

In some cases, the infection may progress without symptoms. In others, onset is marked by fever, general malaise, muscle aches, and a cough, similar to a common respiratory infection.

The disease can develop into a severe form of pneumonia, with high fever, chills, and breathing difficulties. In serious cases, signs of respiratory failure may appear. The course of the illness depends on how quickly a diagnosis is made and on the patient's general state of health. Without timely treatment, legionellosis can cause serious complications and, in the most severe cases, can be fatal.

Who is most at risk

The risk of severe illness is greatest in people with weakened immune systems — particularly the elderly, patients with chronic conditions, and immunocompromised individuals. Workers who spend long periods near air conditioning installations or inadequately maintained water systems are also at heightened risk. The bacterium can infect people of all ages, including children, but severe cases occur more frequently in those with underlying risk factors.

Diagnosis and treatment

Diagnosis is established through laboratory tests, with the fastest method being the Legionella urinary antigen test, which can confirm infection within a few hours. The main challenge remains clinical suspicion, as symptoms can be mistaken for those of other respiratory conditions. It is therefore important for patients to inform their doctor if they have been in environments with air conditioning systems or water networks that may pose a risk.

Treatment is carried out with antibiotics, and its success depends on how quickly a diagnosis is reached. Early diagnosis and treatment reduce the risk of severe complications. Delays can lead to extensive lung damage and respiratory failure, requiring admission to intensive care.

Prevention

There is no vaccine against this infection. The most effective means of prevention is the proper maintenance of air conditioning systems and water installations. Regular upkeep, adherence to hygiene standards in buildings and workplaces, and the swift identification of potential sources of contamination are the most effective ways to reduce the risk of infection. The doctor recommends seeking medical advice at the first appearance of symptoms, particularly for those who have been exposed to such environments.