Legionella bacteria are found naturally in the environment, usually in fresh water. The bacteria grow best in warm water and can be found in hot tubs, cooling towers, hot water tanks, or plumbing of large buildings.

People become infected with Legionella when they breathe in a mist or vapor (small droplets of water in the air) that has been contaminated with the bacteria. One example is breathing in the steam from a whirlpool spa that has not been properly cleaned and disinfected. The bacteria are typically not spread from one person to another person.


People who get sick after exposure to Legionella bacteria usually develop one of two main forms of Legionellosis (or illness from Legionella infection): Legionnaires’ disease or Pontiac fever. Legionnaires’ disease involves pneumonia and can also include symptoms such as cough, shortness of breath, fever, muscle aches, and mild-to-severe- gastrointestinal illness. 

Pontiac fever is a milder respiratory disease that does not include pneumonia. This form of the disease usually resolves on its own. In rare occurrences, extrapulmonary Legionella infections can occur in soft tissue or wounds.  

Clinicians usually order either respiratory culture or urine antigen test to determine if a patient’s pneumonia is caused by Legionella. See “Resources for Healthcare Providers and Clinicians” below for additional information on diagnosis and treatment of Legionellosis.

Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the United States. However, many infections are not diagnosed or reported, so the actual number of illnesses is likely to be higher. More illnesses are reported during the summer and early fall, but they can occur at any time of year.

People at Risk

Legionellosis can affect anyone. However, people most at risk of getting Legionellosis are usually 50 years of age or older, current or former smokers, have a chronic lung disease (like emphysema or chronic obstructive pulmonary disease (COPD)), or have compromised immune systems.

Legionellosis in Georgia

Legionellosis case reports have increased in Georgia over the past several years. This is consistent with regional and national Legionellosis trends. See links in resources for the general public below for the most recent CDC Legionellosis surveillance report and Morbidity and Mortality Weekly Report (MMWR) with Legionellosis counts. 

Reporting Legionellosis

All cases of Legionella infection should be reported to the Georgia Department of Public Health (DPH) within seven days. More about what needs to be reported, who needs to report diseases, and how to report can be found on the DPH Notifiable Disease Reporting page. Public health interviews are attempted for all reported cases to gather information about risk factors and potential exposures for Legionella, including travel history, hospitalizations and healthcare facility visits, and recreational or occupational water exposures 

Outbreaks of Legionnaires' Disease

Outbreaks occur when two or more people become ill following shared exposures, such as patients in hospitals, nursing homes, and long-term care facilities. These types of buildings tend to have complex water systems, and many people in such buildings have underlying illnesses that increase their risk for Legionella infection. Outbreaks can also occur at tourist accommodations (such as on cruise ships, in hotels, and at campgrounds) where people visit. 

Other outbreaks have been linked to aerosol sources in the community, with the most frequently reported sources being whirlpool spas, cooling towers, decorative fountains, and water used for drinking and bathing (such as those in gyms and communal showers).


Healthcare Associated Case Definition

A full Legionella investigation is triggered when a "presumptive" case with ≥10 days of continuous stay at a healthcare facility during the 14 days before onset of symptoms. Possible healthcare-associated Legionnaires’ disease: A case that spent a portion of the 14 days before date of symptom onset in one or more a healthcare facilities, but does not meet the criteria for presumptive healthcare associated Legionnaires' Disease in an institutional or healthcare setting is identified. Examples of such healthcare facilities are: hospitals, long-term care facility, or clinic.  

For more information, please refer to the CDC website:


Travel-Associated Case Definition

Cases of Legionellosis may be associated with travel on a cruise ship or staying overnight in a hotel or other public accommodation. CDC defines travel-associated outbreaks as two or more Legionnaires’ disease cases associated with the same travel accommodation in a 12-month period.

Travel-associated Legionnaires’ disease: A case of Legionnaires’ disease in a patient who has a history of spending at least one night away from home (excluding healthcare settings) in the 14 days before onset of illness. Travel-associated Pontiac fever: A case of Pontiac fever in a patient who has a history of spending at least one night away from home (excluding healthcare settings) in the 3 days before onset of illness.

For more information, please refer to the CDC website:



Protect Yourself

Use humidifiers and all respiratory equipment properly:

  • Always use sterile and/or distilled water
  • Change the water after each use
  • Clean the humidifier every three days
  • Change the filters on a regular basis
  • Follow manufacturers’ cleaning recommendations

Be sure to routinely clean at-home whirlpools and hot tubs according to manufacturers’ recommendations. Also, properly measuring and maintaining safe disinfection levels is important in preventing Legionella growth. See link in “Resources for the General Public” below for a fact sheet on protecting yourself and others from Legionella in hot tubs and spas. 

Legionella can also be found in gardening soils, potting mixes, and mulches. After use, wash your hands with warm, soapy water thoroughly.

Water Management Programs

Owners and managers of healthcare facilities, tourist accommodations, and other high-risk settings, especially those with large, complex plumbing systems, should use water management programs to prevent the growth and spread of Legionella. Check to see if your building and any water features need a WMP. The Centers for Disease Control and Prevention has created a toolkit to help building operators and managers develop a site-specific water management program. See resources for building owners and operators below for the free PreventLD training and WMP toolkit which outline how to create and implement a WMP.

Some preventative measures to take include:

  • Regularly monitoring and maintain water quality parameters, including disinfectant, pH, and temperature levels
  • Disinfecting cooling towers according to recommended guidelines


There are numerous resources, tools, and recommendations that have been developed for Legionella education and prevention. Below are free resources to enhance learning and knowledge of practices to prevent the growth and spread of Legionella

General Public

Healthcare Providers and Clinicians

Public Health 

Building Owners and Operators

Page updated 12/30/2022