Legionnaires' Disease (Air Conditioning Pneumonia): Symptoms and Treatment

Legionnaires' disease, commonly known as air conditioning pneumonia, is a severe lung infection caused by the Legionella bacteria. It typically occurs when people inhale invisible water droplets containing the bacteria, which tend to breed in poorly maintained water systems such as air conditioners, water tanks, and hot tubs. While early diagnosis and appropriate antibiotic treatment can lead to a full recovery, neglecting the condition can be life-threatening, particularly for high-risk groups. Knowing how the cooling systems we frequently rely on to beat the summer heat can threaten our health when used incorrectly is the first step towards prevention.

• The causative agent is the Legionella pneumophila bacterium, which thrives in warm, damp environments.
• It is not transmitted from person to person; it settles in the lungs through the inhalation of infected water droplets.
• High fever, dry cough, muscle aches, and shortness of breath are the most common complaints.
• Not only air conditioners, but also hot tubs, decorative fountains, and large water tanks can be sources of risk.
• Treatment involves specific antibiotics administered in a hospital setting or at home under a doctor's supervision.

What is Legionnaires' Disease (Air Conditioning Pneumonia)?

Legionnaires' disease is a type of atypical pneumonia that causes inflammation in the lungs. The disease takes its name from a major outbreak that occurred in 1976 during an American Legion convention held at a hotel in the United States. Bacteria spreading from the hotel's ventilation system caused numerous attendees to fall ill, and the condition entered medical literature under this name.

The Legionella pneumophila bacteria that cause the disease are naturally found in harmless quantities in freshwater sources like lakes and streams. However, they can multiply rapidly when they infiltrate the complex water systems of large buildings such as hotels, hospitals, shopping centres, or large workplaces. If the immune system fails to destroy the bacteria once they reach the lungs, they multiply and create a severe infection. The disease can present in a wide spectrum, ranging from "Pontiac fever," which features mild flu-like symptoms, to severe pneumonia requiring intensive care.

Causes and Risk Factors

The primary cause of Legionnaires' disease is the inhalation of water droplets (aerosols) harbouring the Legionella bacteria. The bacteria tend to breed rapidly, particularly in warm water between 20°C and 45°C.

Main Sources Where the Bacteria Breed

• Central cooling towers and ventilation systems of large buildings
• Poorly maintained home or vehicle air conditioners
• Hot tubs, heated pools, and thermal spa facilities
• Decorative fountains and waterfalls
• Large water tanks, boilers, and unused showerheads

Who is at Risk?

Not everyone who inhales the bacteria falls ill. A healthy immune system can usually fight off this infection easily. However, certain factors significantly increase the risk of developing the disease. Individuals aged 50 and over, long-term smokers, and those with reduced lung capacity are in the highest risk group. Additionally, people with chronic respiratory conditions such as asthma, COPD (Chronic Obstructive Pulmonary Disease), or emphysema are more vulnerable to the infection. The likelihood of the disease taking a severe course is also high in individuals undergoing cancer treatment, organ transplant recipients, or those with chronic conditions that suppress the immune system, such as diabetes.

Symptoms of Legionnaires' Disease

The incubation period for the disease generally ranges from 2 to 10 days after exposure to the bacteria. At the end of this period, symptoms begin suddenly and can worsen within days. Although the symptoms of Legionnaires' disease are similar to other types of pneumonia, they do have some distinguishing features.

Early Stage Symptoms

Within the first few days, patients typically experience profound fatigue. This is accompanied by widespread muscle and joint pain and a mild headache. Fever can rise rapidly to 39°C and above, often accompanied by severe chills.

Progressive Stage Symptoms

Once the infection is firmly established in the lungs, respiratory complaints take precedence. The cough, which is initially dry, may become productive over time; rarely, blood may be seen in the sputum. A stabbing sensation or pain in the chest when breathing, along with progressive shortness of breath, are common. Unlike other types of pneumonia, digestive system issues such as nausea, vomiting, and diarrhoea are more frequently observed in Legionnaires' disease. In elderly patients, confusion, disorientation, and lethargy may also be seen as the infection affects brain functions.

Transmission Routes and Prevention Methods

Legionnaires' disease is transmitted by inhaling infected water vapour or fine water droplets. The disease does not spread from person to person through coughing or physical contact. Therefore, the primary way to protect against the disease is to ensure the safety of the water and ventilation systems around us.

Precautions for Air Conditioning and Water Systems

The filters of the air conditioners in use must be cleaned or replaced periodically. For central air conditioning systems, it is essential that cooling towers and water tanks are regularly disinfected by professional teams. In homes, showerheads and taps that have not been used for a long time should be flushed with hot water for a few minutes before use. The chlorine or bromine levels and pH values of hot tubs and heated pools must be constantly monitored.

Things to Consider When Using Air Conditioning

Instead of running the air conditioner at extremely cold settings (e.g., 18°C), keeping it at 7-8 degrees lower than the outside temperature—ideally around 23-24°C—prevents your body's resistance from dropping. Moving suddenly from the heat into an air-conditioned environment not only creates an infection risk but can also pose blood pressure risks. You should avoid direct exposure to the cold draught of the air conditioner and direct the airflow towards the ceiling or an empty space. Furthermore, naturally ventilating air-conditioned rooms by opening windows at regular intervals improves indoor air quality.

How is it Diagnosed at the Hospital?

For a patient presenting with suspected Legionnaires' disease, the physician will first conduct a detailed physical examination and listen to the patient's recent travel or air conditioning exposure history. The first step to confirm a lung infection is usually taking a chest X-ray or a computed tomography (CT) scan.

Once the clinical picture of pneumonia is confirmed, specific tests are requested to determine whether the infection is caused by the Legionella bacteria. The most commonly used method that provides the fastest results is the Legionella urinary antigen test. This test detects a specific strain of the bacteria in the urine, allowing for a definitive diagnosis within hours. If necessary, a laboratory culture of a sample taken from the patient's sputum (sputum culture) may be requested. Additionally, comprehensive blood tests are performed to evaluate the severity of the infection and kidney and liver functions.

The Treatment Process

The treatment of Legionnaires' disease requires the use of specific antibiotics targeting the bacteria. The disease will not resolve simply by resting or taking basic cold medications. The earlier treatment is started, the higher the chances of recovery and the lower the risk of complications.

In mild cases, the physician may prescribe oral antibiotics and monitor the patient at home. However, individuals experiencing shortness of breath, a drop in oxygen levels, the elderly, or those with additional chronic diseases must be admitted to the hospital for treatment. In a hospital setting, antibiotics are usually administered intravenously (IV). Oxygen support is provided to patients experiencing respiratory distress, and intravenous fluids are given to prevent dehydration. The treatment period generally lasts 10 to 14 days, although this may be extended for individuals with a weakened immune system. Even after being discharged from the hospital, it can take several weeks for patients to regain their former energy and fully recover.

Possible Complications and Risk Groups

If not treated promptly and correctly, Legionnaires' disease can trigger a chain reaction in the body, threatening vital organs. When the bacteria cause severe damage to lung tissue, the most common complication is respiratory failure. The lungs become unable to supply enough oxygen to the blood, and the patient may need to be placed on a breathing machine (ventilator).

The progression of the disease can cause the kidneys to suddenly lose their ability to filter blood, leading to acute kidney failure. One of the most dangerous scenarios is septic shock. As the infection enters the bloodstream, blood pressure drops suddenly, blood flow to vital organs decreases, and multiple organ failure can develop. The risk of these complications developing—and the associated threat to life—is particularly high in individuals over 65 and immunocompromised patients.

When to See a Doctor?

It is vital not to dismiss symptoms that begin during periods of heavy air conditioning use or after a hotel/thermal spa holiday as a simple cold. If you experience one or more of the following symptoms, you should consult a healthcare facility without delay:

• Persistent high fever that does not drop below 39°C despite fever-reducing medications
• Severe shortness of breath felt even while resting, or rapid breathing
• A stabbing sensation or severe pain in the chest when breathing or coughing
• Blood in the sputum
• Confusion, disorientation, or excessive drowsiness

Particularly in the event of a bluish tint to the lips or nail beds (a sign of oxygen deprivation) and severe shortness of breath, you should immediately call the 112 Emergency Call Centre to request an ambulance.

The Process at BHT CLINIC

At the BHT CLINIC İstanbul Tema Hastanesi Pulmonology (Chest Diseases) department, the diagnosis and treatment of Legionnaires' disease and all other respiratory infections are meticulously carried out by our expert medical staff. In our hospital, the urinary antigen tests, high-resolution chest CT scans, and pulmonary function tests required for rapid diagnosis are performed using the most advanced technologies.

When necessary, advanced diagnostic methods such as Bronchoscopy and EBUS are also successfully performed. For emergencies like sudden shortness of breath and high fever, we are always by your side with our 24/7 Emergency Department and fully equipped Intensive Care Units. Bringing any previous chest X-rays and a list of medications you are currently taking to your consultation will help speed up the process. To get detailed information and consult our specialist doctors, you can easily book through our appointment page.

Frequently Asked Questions

Is Legionnaires' disease contagious?

No, Legionnaires' disease is not transmitted from person to person. The disease is only contracted by inhaling water droplets or water vapour carrying the Legionella bacteria. It is not possible to catch the infection from another patient in the same room through coughing, sneezing, or physical contact.

What is the difference between an air conditioning cold and Legionnaires' disease?

An air conditioning cold is a temporary and mild condition, such as muscle stiffness, a mild headache, or a runny nose, that develops due to direct exposure to cold air. Legionnaires' disease, on the other hand, is a bacterial lung infection; it presents with a high fever exceeding 39°C, severe shortness of breath, and pneumonia, and absolutely requires medical treatment.

How long does it take to recover from the disease?

When diagnosed early and started on appropriate antibiotic treatment, patients generally begin to feel better within a few days. Antibiotic treatment administered in the hospital or at home lasts 10-14 days. However, it can take anywhere from a few weeks to a month for the patient to fully regain their energy and for the lungs to completely recover.

Do home air conditioners carry a risk of Legionnaires' disease?

Home (split) air conditioners carry a much lower risk compared to central systems because they do not use water cooling towers. However, moisture and dust accumulating in the indoor units can create a breeding ground for bacteria and fungi if the filters are not cleaned for a long time. Therefore, the filters of home air conditioners should also be cleaned and maintained regularly.

This article is for informational purposes only; please consult your physician for diagnosis and treatment.