The cooling towers from which the people were infected in the latter outbreak had been cleaned during the summer outbreak, raising concerns about how well the bacteria could be controlled.On 28 August 2015, an outbreak of Legionnaires disease was detected at San Quentin State Prison in Northern California; 81 people were sickened and the cause was sludge that had built up in cooling towers.Between June 2015, and January 2016, 87 cases of Legionnaires disease were reported by the Michigan Department of Health and Human Services for the city of Flint, Michigan, and surrounding areas. The outbreak may have been linked to the Flint water crisis, in which the citys water source was changed to a cheaper and inadequately treated source. Ten of those cases were fatal.In November 2017, an outbreak was detected at Hospital de São Francisco Xavier, Lisbon, Portugal, with up to 53 people being diagnosed with the disease and five of them dying from it.In Quincy, Illinois, at the Illinois Veterans Home, a 2015 outbreak of the disease killed 12 people and sickened more than 50 others. It was believed to be caused by infected water supply. Three more cases were identified by November 2017.In the autumn of 2017, 22 cases were reported in a Legionnaires disease outbreak at Disneyland in Anaheim, California. It was believed to have been caused by a cooling tower that releases mist for the comfort of visitors.
Sources where temperatures allow the bacteria to thrive include hot water tanks, cooling towers, and evaporative condensers of large air conditioning systems, such as those commonly found in hotels and large office buildings. Though the first known outbreak was in Philadelphia, cases of legionellosis have occurred throughout the world. Reservoirs
L. pneumophila thrives in aquatic systems, where it is established within amoebae in a symbiotic relationship. Legionella bacteria survive in water as intracellular parasites of water-dwelling protozoa, such as amoebae. Amoebae are often part of biofilms, and once Legionella and infected amoebae are protected within a biofilm, they are particularly difficult to destroy.In the built environment, central air conditioning systems in office buildings, hotels, and hospitals are sources of contaminated water. Other places the bacteria can dwell include cooling towers used in industrial cooling systems, evaporative coolers, nebulizers, humidifiers, whirlpool spas, hot water systems, showers, windshield washers, fountains, room-air humidifiers, ice-making machines, and misting systems typically found in grocery-store produce sections.The bacteria may also be transmitted from contaminated aerosols generated in hot tubs if the disinfection and maintenance programs are not followed rigorously. Freshwater ponds, creeks, and ornamental fountains are potential sources of Legionella. The disease is particularly associated with hotels, fountains, cruise ships, and hospitals with complex potable water systems and cooling systems. Respiratory-care devices such as humidifiers and nebulizers used with contaminated tap water may contain Legionella species, so using sterile water is very important. Other sources include exposure to potting mix and compost. Mechanism
Legionella spp.