Legionnaires’ disease is caused by the Legionella bacteria, which is a naturally occurring aquatic organism. Illness results from exposure to contaminated water aerosols or from aspirating contaminated water. In general, it is not spread from person to person. The disease is a serious lung infection (pneumonia) that is deadly in about 10% of the people who get it.
Outbreaks and Environmental Risk Factors
The CDC reported that there are approximately 20 outbreaks of Legionnaires disease reported each year, and that the number of cases has been growing over the past few years. Most identified outbreaks are in buildings with large water systems, such as hotels, long-term care facilities, apartment complexes, and hospitals. Cruise ships are another place where outbreaks have occurred. Legionella grows best in building water systems that are not well maintained. CDC investigations show that almost all outbreaks were caused by problems that were preventable with more effective water management. At our hospital, we have a robust water management program that includes regular testing and treatments to help prevent the growth of Legionella.
People Most at Risk
People most at risk for getting Legionnaires’ disease are adults 50 years or older. Current or former smokers and people with chronic lung disease, such as emphysema, also have a higher risk. Immunocompromised (caused by diseases or medications) patients in general hospitals are at greater risk of infection. Healthcare providers should tell patients if they are at increased risk for pneumonia and advise them to seek care quickly if they develop symptoms of pneumonia. Patients who present with serious pneumonia, especially those requiring intensive care or who recently were in a healthcare facility or hotel or on a cruise ship, should be tested for Legionnaires’ disease.