Legionella: What Do We Need to Know?

Posted August 11, 2015

Currently, New York City is facing an outbreak of Legionnaires’ disease, with 100 people sickened from the illness since early July. Ten of the affected individuals have died from the disease.

Legionnaires’ disease is a severe and often lethal form of pneumonia that is spread via exposure to water droplets that contain the bacteria Legionella. Such exposure comes from inhaling contaminated fine water mists from cooling towers, hot tubs, showers, faucets, decorative water fountains, or other water sources. According to the Centers for Disease Control and Prevention, the mortality rate of the disease ranges from 5 to 30 percent. Survivors of the illness often require extensive medical treatment and could face long-lasting health effects.

One of the largest and most common sources of Legionella is cooling towers (heat rejection equipment used in air conditioning and industrial cooling water systems). Many governmental agencies, cooling tower manufacturers, and industrial trade organizations have developed design and maintenance guidelines for controlling the growth and proliferation of Legionella within cooling towers.

Early last year, AIHA's Indoor Environmental Quality (IEQ) Committee recognized a need for more comprehensive guidance on the routine assessments and approaches to effective Legionella control measures. The resulting publication, Recognition, Evaluation, and Control of Legionella in Building Water Systems, was recently published in May of this year.

So as authorities respond to the outbreak in New York, what can you do to protect yourself, your coworkers, and those close to you?

Be informed. Legionnaires’ disease is not transmitted from person-to-person, so seeing the outbreak spread to other areas of the country from the Bronx is highly unlikely. The bacterium is primarily found in contaminated water sources, such as reservoirs of warmer water, cooling towers for air conditioning systems, and water distribution centers.  The association with air condition systems often causes people to believe there is a risk of catching Legionnaires’ disease from the cold air blowing from your home or work air conditioner.  That is not the case.  Legionella grows in the part of the air conditioning system that is outside of commercial buildings and does not mix with the air that blows through the building.  Exposure to cooling tower mists most frequently occurs when walking outside of a building with a contaminated cooling tower. 

Most people exposed to the bacteria do not become ill. Certain people are considered higher risk for contracting the disease: the elderly, those with chronic lung disease, smokers, and individuals who have weakened immune systems. If you have reason to believe you were exposed to the bacteria, contact your doctor or local health department. Be sure to mention if you have traveled in the last two weeks. A person diagnosed with Legionnaires' disease in the workplace is not a threat to others who share office space or other areas with him or her. However, if you believe that your workplace was the source of the illness, contact your local health department.

Prevent infection by practicing standard good health habits. Don't smoke. Get a flu vaccine and seek medical attention if you have flu-like symptoms. If you use or own a hot tub, make sure the hot tub has the right disinfectant and pH levels—high water temperatures make it difficult to maintain the proper disinfectant levels needed to kill bacteria and germs like Legionella.

Beware of decorative water fountains. The Legionella bacteria has a higher chance of being found in decorative pools or fountains, water walls, and spray misting systems that are not intended as a source of drinking water and are poorly maintained.

Industrial hygienists are among the front-line responders to such outbreaks. With their experience and skillsets, they are already being called upon to perform proactive assessments and evaluate preventive and remedial measures. Using guides such as the new AIHA guideline, IH professionals are trained to recognize workplace hazards such as Legionella and managing the risks it presents to keep workers and members of the public safe.

On September 15, AIHA will be hosting an Introduction to the Recognition, Evaluation and Control of Legionella in Building Water Systems Guideline. This introductory webinar is intended for everyone who should know more about Legionella and the risks it poses to workers, visitors and the general public. Managers, building owners, industrial hygienists, environmental health professionals, and public health officials involved with the investigation of Legionnaires’ disease would all benefit from information presented.