Legionella – Basic Information

Chillicothe, OH – As of this release, there have been no presumptive healthcare associated cases of Legionnaires’ disease in Ross County residents in 2023. In the last decade, there have been no general Legionella outbreaks or healthcare associated outbreaks of Legionella in Ross County.

Legionella are bacteria that grow naturally in the environment. Legionella can be found in many types of water systems, but reproduce more in warm, stagnant water. It is dispersed through aerosolization of water droplets containing the bacteria. Legionellosis is an infection caused by the bacterium Legionella pneumophila.

According to the Ohio Department of Health’s (ODH) Infectious Disease Control Manual (IDCM), a legionellosis outbreak is defined as two or more cases within a 12-month period with exposure to the same location. When a laboratory result is positive for Legionella, the result is automatically sent through the ODH Disease Reporting System to the appropriate local health department. If any of the cases are deemed a presumptive healthcare associated case, a full investigation is conducted. Ross County averages five cases of legionellosis a year.

Legionella can enter your body when breathing in small droplets of water in the air that contain the bacteria. The disease has two distinct forms. A serious type of pneumonia caused by the Legionella bacteria is called Legionnaires’ disease and a milder infection of the upper respiratory tract is called Pontiac fever. According to the Center for Disease Control and Prevention (CDC), in general people do not spread Legionnaires’ disease and Pontiac fever to other people.

An estimated 8,000 to 18,000 persons get Legionnaires’ disease in the United States each year. Outbreaks of Legionnaires’ disease have received the most media attention; however, most often the disease occurs as single, isolated cases not associated with any recognized outbreak. Outbreaks are usually recognized in the summer and early fall, but cases may occur year-round.

Additional information on legionellosis including diagnosis, prevention, and treatment can be found at www.cdc.gov/legionella.