Legionella

What is Legionella?

It is a bacterium of the genus Legionella, capable of causing a form of pneumonia known as Legionnaires’ disease.

These bacteria exist in natural freshwater and warm-water ecosystems. They are often found in man-made ecological niches: building water systems, HVAC equipment (air conditioning systems), hot springs, fountains, and other environments capable of forming aerosols (they grow and multiply at an optimal temperature between 35˚C and 45˚C).

How does transmission and infection occur?

There is no person-to-person transmission, nor does it occur through the ingestion of contaminated water.

Infection occurs through inhalation (via the respiratory tract) of aerosols contaminated with the bacteria, via household showers, cooling towers, HVAC systems, hot tubs, saunas, and jacuzzis.

Inhalation of contaminated droplets can reach the lungs, triggering the infection. The occurrence of infection depends on several factors: the concentration and virulence of the strain, and host risk factors.

What are the symptoms and diseases caused by this bacterium?

These infections may be asymptomatic or present with symptoms.

The symptoms are nonspecific: fatigue, nausea, cough, shortness of breath, high fever, muscle aches, and headaches.

In the case of the milder form—Pontiac fever—patients do not develop pneumonia, and symptoms may last 2 to 5 days.

In the more severe form—Legionnaires’ disease—patients develop pneumonia, and symptoms last 2 to 14 days.

Who are the at-risk groups?

When infected with Legionella, the groups most at risk for severe infection are:

• People over 50 years of age;
• Regular smokers;
• People with chronic lung diseases (COPD and emphysema);
• Patients with weakened immune systems due to cancer, kidney disease, or diabetes;
• Patients taking medication to suppress (weaken) the immune system (transplant recipients, chemotherapy patients).

What about children?

Legionella is not a common microorganism in children with pneumonia.

Cases of Legionella infection in children are very rare.

Is there a vaccine?

There is no vaccine to prevent the disease.

Prevention with antibiotics is also not effective.

How is Legionnaires’ disease diagnosed?

Most people with Legionnaires’ disease develop severe pneumonia (a lung infection), as Legionella grows and multiplies in the lungs. Pneumonia is confirmed by radiological/imaging tests (chest X-ray), a physical examination of the patient, and laboratory tests.

Several laboratory tests can be performed to detect Legionella.

The most common and widely used laboratory test involves detecting components of the bacterium in a urine sample (antigenuria) using specific antibodies. It is a rapid test that is highly sensitive and specific.

A positive urine test for Legionella in a patient with pneumonia confirms the diagnosis of Legionnaires’ disease.

Other tests, which take longer and are not routinely used, also confirm Legionnaires’ disease:

• Growth of Legionella bacteria in appropriate culture tests using respiratory samples (sputum and others)
• The presence of rising antibody levels in blood samples collected shortly after the onset of symptoms and during recovery (two samples taken 10 days apart).

Is there a treatment?

Yes, treatment involves antibiotics.

The test I can perform is:

L. pneumophila Antigen Test.
See the test description in the Collections Manual

Where can I get the test done?

Find a Collection Point to have the test done: Collection Points

Legionella Outbreak

What is an outbreak?

It is an epidemiological term used to describe an above-normal number of infection cases in infectious or public health diseases.

Outbreaks occur in specific locations (institutions, schools, homes, commercial kitchens, buildings, neighborhoods, or communities) and are associated with the hypothesis that these locations share a common factor:

• The same source of infection or contamination;
• The same risk factor;
• The same clinical presentation;
• Simultaneous occurrence.

Should I be concerned about this outbreak?

The outbreak is linked to three parishes in the southern part of the municipality of Vila Franca de Xira: Vialonga, Forte da Casa, and Povoa de Santa Iria.

If you live in or have been in the designated area and are experiencing the described symptoms, you should contact your primary care physician or call the Health Hotline at 808 24 24 24, which has been set up for this purpose.

What preventive measures should I take?

The Directorate-General for Health advises that, in the affected areas, the following preventive measures be taken: opt for baths rather than showers, and avoid using hot water and high water pressure.

As a preventive measure, showerheads should be disinfected by soaking them in a solution of water and bleach for 30 minutes once a week.

In water heaters, the temperature should be set to 75°C.

Also avoid saunas, whirlpools, and hot tubs.

Tap water is safe to drink and use for cooking.