A Severe Pneumonia with a Specific Cause
Legionnaires' disease is a serious lung infection caused by a bacterium called Legionella. The illness got its name after a 1976 outbreak at an American Legion convention in Philadelphia, where many attendees fell ill. Unlike the flu or the common cold,
Legionnaires' disease is not spread from person to person. You cannot catch it from someone who is sick. Instead, the infection comes from an environmental source. While it can be severe, requiring hospitalization, it's important to know that most healthy people exposed to the bacteria do not get sick. The bacteria can also cause a milder, flu-like illness called Pontiac fever, which typically resolves on its own.
How You Get It: Inhaling Contaminated Mist
People contract Legionnaires' disease by breathing in small water droplets, or aerosols, that are contaminated with Legionella bacteria. Swallowing contaminated water does not typically cause infection, unless it is accidentally aspirated, or goes “down the wrong pipe” into the lungs. The Legionella bacteria exist naturally in freshwater environments like lakes and streams, but they become a public health issue when they grow and multiply in man-made water systems. Common sources of outbreaks include large plumbing systems, cooling towers for air conditioning systems in large buildings, hot tubs, decorative fountains, and shower heads. Outbreaks have been linked to hotels, hospitals, and cruise ships, where complex water systems can harbor the bacteria if not properly maintained.
Recognizing the Symptoms
The symptoms of Legionnaires' disease usually appear between two to 14 days after exposure and are similar to other types of pneumonia. They often start with a headache and muscle aches, followed by high fever (which can exceed 104°F), a persistent cough, and shortness of breath. Other symptoms can include confusion, diarrhea, nausea, and chest pain. Because these symptoms mimic other respiratory illnesses, a specific laboratory test is required for a definitive diagnosis. Early diagnosis and treatment are crucial for a successful recovery and to prevent serious complications.
Who Is Most at Risk?
While anyone can get Legionnaires' disease, some groups are significantly more vulnerable. The primary risk factors include being age 50 or older, being a current or former smoker, or having a weakened immune system from conditions like cancer, kidney disease, or from taking certain medications like steroids or transplant anti-rejection drugs. People with chronic lung disease, such as COPD, are also at increased risk. It is relatively uncommon for a healthy young person to contract Legionnaires' disease, even if exposed to the bacteria.
Prevention and Treatment
The key to preventing Legionnaires' disease is managing the water systems where the bacteria thrive. Building owners and managers are responsible for maintaining and disinfecting their water systems, including cooling towers, plumbing, and hot tubs, to limit Legionella growth. There is no vaccine to prevent the disease. For individuals, the risk is generally low and not something that requires daily vigilance, but being aware of the sources is helpful. If infection does occur, Legionnaires' disease is treatable with common antibiotics, such as azithromycin or a fluoroquinolone like levofloxacin. Treatment is most effective when started promptly, and most people who receive timely hospital care make a full recovery.
