- Disease Background — The bacteria got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of this disease, a type of pneumonia (lung infection). Subsequently, the bacterium causing the illness was named Legionella pneumophila and later, the name of the illness was changed to legionellosis.Between 8,000 and 18, 000 patients are hospitalized annually in the United States with legionellosis. Legionella bacteria can cause infection any time during the year, with the peak number of illnesses occurring in summer and early autumn.As with many lung-related illnesses, those at greatest risk of getting sick are the elderly, people who smoke or drink heavily, and those who have chronic lung disease, such as emphysema, chronic obstructive pulmonary disease, etc.People with compromised immune systems (from HIV, cancer, diabetes, kidney disease, chemotherapy, organ transplant, etc.) are also more susceptible to contracting legionellosis, as well as many other communicable or environmental diseases.Since the disease can show up early with very nonspecific signs and symptoms, such as a high fever, chills and a cough, it can be hard to diagnose. Some people get muscle aches, headaches and gastrointestinal symptoms. Legionnaires’ disease looks a lot like many other cases of community-associated pneumonia, so it is often missed upon initial diagnosis. This can lead to underreporting of actual legionellosis cases.
Only laboratory testing can confirm the organism making a patient ill. In the case of suspected legionellosis, these tests can include cultures or polymerase chain reaction (PCR) tests on sputum, blood or lung tissues. The urine antigen test is the easiest and most frequently used.
Legionella infection can result in either Legionnaires’ disease or a milder form of illness called Pontiac fever. To become infected, an individual needs to be both susceptible to infections and exposed to the microorganism, Legionella pneumophila. Legionella pneumophila causes more than 90 percent of infections. The incubation period varies widely, from five to 66 hours for Pontiac fever to two to 10 days for Legionnaires’ disease.
People get Legionnaires’ disease when they breathe in aerosolized water, mist, or vapor that has been contaminated with Legionella. Aerosols are created when water breaks up into small enough parts that can be breathed in.
Since Legionella bacteria are widespread in natural and man-made environments, they can enter facilities in small numbers through the water system. They can then grow within the biofilm of the water supply system in areas of the facility where the water is held in a range of 77° F to 108° F. Such areas within public accommodation facilities include cooling towers, spas, whirlpools, fountains and showers. All of these areas have been sources of Legionnaires’ disease outbreaks.
- Outbreaks in Southern Nevada — Between 2000 and 2012, the health district investigated seven outbreaks of legionellosis among travelers to Las Vegas. In two of the seven investigations, the clinical isolates of Legionella bacteria obtained from the respiratory tracts of people diagnosed with Legionnaires’ disease were linked with environmental isolates of Legionella bacteria taken from the water within the public accommodation facilities where the individuals stayed as guests.
- Legionella Surveillance and Reporting — There has been an increased frequency of reported travel-associated outbreaks of legionellosis that have been publicized by the media. The increase can be attributed to improved national surveillance to detect travel-associated Legionnaires’ disease.This enhanced national surveillance system involves all states reporting cases of legionellosis to the Centers for Disease Control and Prevention (CDC) and the CDC providing information back to states about any patients who had travelled to other states during the weeks before they became ill.The medical tests for diagnosing legionellosis have improved and become widely available, assisting doctors in accurate diagnosis. When Legionnaires’ disease is diagnosed, the doctor is required by law to report the case to the health district. The district then investigates the case, identifies water-related exposures that could have been the source of Legionella and whether they were associated with travel, and reports the details to the state health department. The state health department then reports the case to the CDC.If it is discovered that the ill individual had travelled during the two weeks before the onset of symptoms, the CDC then shares information about the case with the state public health department(s) of the state(s) where the patient visited to help identify possible outbreaks. If the case reports travel to Clark County, the CDC reports the case information directly to the health district.
Phone: (702) 759-0677
Updated on: July 23, 2021