Learn About Legionnaires' Disease

Legionnaires’ disease was named after a 1976 outbreak at a Pennsylvania American Legion convention, where a new bacterium, Legionella pneumophila, was identified as the cause. Various strains of this bacteria exist, but not all are associated with the disease, making testing complex. The CDC states there are roughly 5,000 U.S. cases annually, though OSHA estimates it’s closer to 25,000, with most going unreported. A staggering 96% of these cases are sporadic. Most cases are traced back to drinking water systems, with the bacteria found in both natural and man-made water systems. They thrive in warm, stagnant water, particularly between 90° and 105°F. Legionnaires’ disease isn’t airborne; it’s contracted by inhaling or aspirating water droplets containing the bacteria. Cases have quadrupled from 2000 to 2014, with aging infrastructure and water conservation methods partly to blame. While most cases are unique, around 5% result from outbreaks.

Disease symptoms emerge within 2-10 days after exposure to contaminated water droplets. Initial symptoms resemble the flu, but can progress to severe pneumonia-like symptoms including fever, cough, shortness of breath, and chest pain. Other symptoms can include fatigue, diarrhea, and muscle aches. People over 50, smokers, those with lung diseases like emphysema, or those immunocompromised due to conditions like cancer or diabetes, are at higher risk. Several tests can identify the disease. The CDC’s ELITE Program standardizes Legionella isolation techniques for laboratories, with a list of proficient laboratories available.

Legionnaires’ disease is primarily treated with antibiotics, and early treatment typically leads to recovery. At the first symptom onset, it’s crucial to see a doctor. According to the National Institutes for Health, moderate to severe cases require 7–10 days of levofloxacin or azithromycin. Immunocompromised patients might need extended courses, with treatments ranging from 3–21 days, depending on severity and complications. It’s recommended that antibiotics continue until the patient is stable and fever-free for at least 48 hours. More details can be found in the study by Viasus D, et al., 2022. In addition to antibiotics, patients should rest, use a room humidifier, and stay hydrated.

To substantially prevent Legionnaires’ disease, the primary strategy is halting the entry of Legionella bacteria into our water systems, as emphasized by the CDC. Public officials must recognize the risks from our public water systems, promoting dialogue and actions towards improved water system management. This entails infrastructure replacement in areas with failing systems, maintaining effective chlorine levels throughout the distribution system, and establishing risk management for bacterial containment. Public notifications during disruptions are vital, as is comprehensive testing to grasp bacterial threats. At the household and building level, prevention includes addressing stagnant water, adjusting water temperatures, and following CDC-recommended water management programs. Community education on bacterial risks is crucial. Legionella is a water management issue; prevention should begin outside the building, with building-level water management complementing this. Thorough investigations of Legionnaires’ disease cases and more research on water management are essential.

COVID-19 Notes:

Coronavirus disease 2019, more commonly known as COVID-19, is an infectious illness with many symptoms that are similar to Legionnaires’ disease.  During this recent pandemic, our healthcare system was focused on COVID-19 and we are seeing many infections that occurred along with the coronavirus. As a part of dealing with the ongoing COVID-19 concerns, it will be important for healthcare providers to consider additional concerns with significant and ongoing lung symptoms.  

Discuss Legionnaires' Disease Testing with a Healthcare Provider for Post-COVID Care Optimization

Legionella and Garden Soils

Commercial garden soils which include packaged potting mixes and bulk soil supplies have been associated with several cases of Legionnaires’ Disease in WA, as a result of exposure to the bacteria Legionella longbeachae. 

Preventative strategies for this disease are limited to educating the community on the safe use of garden soils, which includes publishing health warnings on bagged materials and providing signage near bulked products. Such warnings attempt to inform the consumer to take precautionary measures when handling garden soils.

Prompt Legionnaires' Disease Testing Vital in Pneumonia Diagnosis: CDC Guidelines

For the Public:

If you are beginning to notice any of the symptoms below, contact your preferred medical professional immediately. Symptoms can take 2 to 10 days :


Listen to Gwen Hanlon

Gwen Hanlon, one of the Board of Directors for Prevent Legionnaires, tells the story of her husband Kevin Hanlon, and their experience with Legionnaires' Disease. Listen today.