A Legionella bacterium causes Legionnaire disease, a serious form of pneumonia that can affect the lungs, the brain, and the digestive system. It can be life-threatening if left untreated for too long. In this blog post, we will discuss what causes Legionnaire disease, what are its symptoms, how it is diagnosed, how it is treated, and how it can be prevented.
Legionnaire disease is caused by inhaling or aspirating water droplets that are contaminated with Legionella bacteria. These bacteria can grow and multiply in warm, moist environments, such as:
Air conditioning systems
Hot tubs and spas
Showers and faucets
Cooling towers
Fountains and misters
Humidifiers and nebulizers
Legionnaire disease is not contagious and cannot be spread from person to person. However, it can cause outbreaks when many people are exposed to the same source of infection.
The symptoms of Legionnaire disease usually start 2 to 14 days after exposure to Legionella bacteria. They can vary from mild to severe, depending on the person’s age, health, and immune system. The most common symptoms are:
Fever (often over 104°F or 40°C)
Cough (usually dry)
Shortness of breath
Muscle aches
Headache
Diarrhea
Nausea
Confusion
Some people may also have chest pain, coughing up blood, abdominal pain, or skin infections. In rare cases, Legionnaire disease can affect the heart, the kidneys, or the nervous system, leading to complications such as:
Respiratory failure
Septic shock
Acute kidney failure
Encephalitis or meningitis
Legionnaire disease can be difficult to diagnose because its symptoms are similar to other types of pneumonia. To confirm the diagnosis, the doctor may perform one or more of the following tests:
Physical examination: The doctor will check the person’s vital signs, listen to their lungs, and look for signs of infection.
Blood tests: The doctor will check the person’s white blood cell count, electrolytes, and kidney function. The doctor may also test the person’s blood for antibodies or DNA of Legionella bacteria.
Urine tests: The doctor will test the person’s urine for antigens of Legionella bacteria. This is a quick and easy test that can detect most cases of Legionnaire disease.
Sputum tests: The doctor will collect a sample of the person’s sputum (mucus from the lungs) and culture it for Legionella bacteria. This test can take several days to get the results, but it can identify the specific type of Legionella bacteria that caused the infection.
Chest X-ray: The doctor will take an X-ray of the person’s chest to look for signs of pneumonia, such as fluid or inflammation in the lungs.
It is common to use antibiotics to treat Legionnaire disease because they can kill or stop the Legionella bacteria from growing. A person's age, health, and severity of the infection determine what type and duration of antibiotic therapy to use. Common antibiotics used to treat Legionnaire disease include:
Levofloxacin
Azithromycin
Doxycycline
Erythromycin
Rifampin
The person may need to take the antibiotics for 7 to 21 days, either orally or intravenously. The person may also need supportive care, such as:
Oxygen therapy
Fluids and electrolytes
Pain relievers
Fever reducers
Anti-nausea medications
In severe cases, the person may need intensive care, such as:
Mechanical ventilation
Dialysis
Blood pressure support
Intravenous immunoglobulin
There is no vaccine available to prevent Legionnaire disease. However, there are some measures that can be taken to reduce the risk of exposure to Legionella bacteria, such as:
Maintaining the temperature of water below 20°C or above 60°C, as the bacteria survive in warm contaminated water.
Cleaning and disinfecting water systems regularly, especially in large buildings, hotels, hospitals, and spas.
Replacing filters and cleaning humidifiers and nebulizers frequently.
Avoiding smoking, as it can damage the lungs and make them more susceptible to infection.
Seeking medical attention promptly if symptoms of pneumonia develop, especially after traveling or staying in a place with a potential source of Legionella bacteria.
