List of Legionnaires' disease outbreaks

List of Legionellosis outbreaks

Year	City	Venue	Source	Cases	Deaths	Fatality rate	Notes
1976	Philadelphia, Pennsylvania	1976 Philadelphia legionellosis outbreak	Air conditioning	221	34	15.4%	This was the eponymous outbreak and probably the deadliest recorded outbreak yet.
1999	Bovenkarspel, Netherlands	1999 Bovenkarspel legionellosis outbreak	Hot tub	318	32	10%	In March 1999, an outbreak in the Netherlands occurred during the Westfriese Flora flower exhibition in Bovenkarspel. 318 people became ill and at least 32 people died. There is a possibility that more people died from it (which might make it the deadliest recorded outbreak), but these people were buried before the Legionella infection was recognized. The source of the bacteria was a hot tub in the exhibition area.
1985	Stafford, England, United Kingdom	Stafford District Hospital	Air conditioning	175	28	16%	In April 1985, 175 patients were admitted to the District or Kingsmead Stafford Hospitals with chest infection or pneumonia. A total of 28 people died. Medical diagnosis showed that Legionnaires' disease was responsible and the immediate epidemiological investigation traced the source of the infection to the air-conditioning cooling tower on the roof of Stafford District Hospital. A Government Inquiry was convened to investigate how the infection occurred and why it became Britain's largest epidemic of Legionnaires' disease. The infection was linked to one small zone in the hospital: the outpatients department. The initial investigation searched for engineering reasons to explain why this particular zone was the risk area. More detailed and wider epidemiological surveys subsequently showed that staff working in the whole area supplied with fresh air taken adjacent to the tower, had antibodies to the disease. The outpatients department was unique in having a very large transient population of susceptible individuals either receiving treatment or accompanying friends.
2005	Toronto, Canada	Seven Oaks Home for the Aged	Cooling tower	127	21	16.5%
2012	Québec City, Canada	Lower Québec City	Possibly cooling towers	180	13	7.22%	180 confirmed cases as of September 14, 2012, probably due to contaminated water in industrial cooling towers.
2005	Fredrikstad, Norway	factory	Air scrubber	56	10	17.8%	56 people became ill and ten died from Legionnaires' disease caused by bacteria growing in an air scrubber of a nearby factory.
2002	Barrow-in-Furness, UK	2002 Barrow-in-Furness legionellosis outbreak	Air conditioning	172	7	4.1%	In 2002, Barrow-in-Furness in the U.K. suffered an outbreak of Legionnaires' disease. Six women and one man died as a result of the illness; another 172 people also contracted the disease. The cause was found to be a contaminated cooling tower at the town's Forum 28 arts centre. Barrow Borough Council later became the first public body in the UK to be charged with corporate manslaughter but were cleared. They were, however, along with architect Gillian Beckingham, fined for breaches of Health and Safety regulations in a trial that ended in 2006.
2001	Murcia, Spain	Hospital		800	6	0.8%	The world's largest outbreak of Legionnaires' disease happened in July 2001 with patients appearing at the hospital on July 7, in Murcia, Spain. More than 800 suspected cases were recorded by the time the last case was treated on July 22; 636–696 of these cases were estimated and 449 confirmed (so, at least 16,000 people were exposed to the bacterium) and 6 died . A case-fatality rate of approximately 1%.
2000	Melbourne, Australia	Melbourne Aquarium	Cooling tower	125	4	4.2%	In April 2000, an outbreak of Legionella pnemophila serogroup 1 occurred in Melbourne, Australia. The outbreak resulted in 125 confirmed cases of Legionnaire's disease, with 95 (76%) hospitalised. It is reported that 4 died from the outbreak. The investigation traced the source of the infection to the cooling tower at the newly opened aquarium. Since this outbreak, legionella infection statistics are required to be reported by the state government as a notifiable disease. Stringent Regulations were introduced by the State to control legionella in 2001.
2012	Calp, Spain	AR Diamante Beach Hotel		18	3	17%	Origin unknown at present. Large hotel with solar water heating system for spa and domestic hot water.
2012	Edinburgh, Scotland, UK	South west of Edinburgh	Possibly cooling towers	99	3	3%	50 confirmed cases, with 49 additional suspected cases. Three people are known to have died from the outbreak.
2012	Chicago, Illinois	JW Marriott Hotel	Decorative Lobby Fountain	10	3	30%	8 confirmed cases with people who stayed at the JW Marriott Chicago during July–August 2012.
2008	New Brunswick, New Jersey	Saint Peter's University Hospital	Drinking water	6	2	33.3%	Chlorination in the water system had dropped below effective levels.
2010	Wales, United Kingdom	South Wales Valleys	Likely cooling towers	22	2	9%	Thought to be cooling towers in local industry.
2012	Auckland, New Zealand	Unknown	Water Source and/or Air Conditioning	11	1	9%	The number of people affected in a major outbreak of Legionnaires' disease in Auckland, which has claimed one life, has risen to 11.
2012	Stoke-on-Trent, England	Warehouse, Fenton	Hot tub	19	1	5.2%	Infection began in warehouse hot tub. Seventeen of the confirmed cases visited the warehouse a couple of weeks before becoming ill.
2011	Los Angeles, California	Playboy Mansion	Hot tub	200	0	0%	200 fallen ill after a four-day conference that culminated in a fundraiser at the Playboy Mansion

Action levels

The European Working Group for Legionella Infections (EWGLI) was established in 1986 within the European Union framework to share knowledge and experience about potential sources of Legionella and their control. This group has published guidelines about the actions to be taken to limit the number of colony forming units (i.e., the "aerobic count") of micro-organisms per mL at 30 °C (minimum 48 hours incubation):

Aerobic count	Legionella	Action required
10,000 or less	1,000 or less	System under control.
more than 10,000 up to 100,000	more than 1,000 up to 10,000	Review program operation. The count should be confirmed by immediate re-sampling. If a similar count is found again, a review of the control measures and risk assessment should be carried out to identify any remedial actions.
more than 100,000	more than 10,000	Implement corrective action. The system should immediately be re-sampled. It should then be 'shot dosed' with an appropriate biocide, as a precaution. The risk assessment and control measures should be reviewed to identify remedial actions.

Almost all natural water sources contain Legionella and their presence should not be taken as an indication of a problem. The tabled figures are for total aerobic plate count, cfu/ml at 30 °C (minimum 48 hours incubation) with colony count determined by the pour plate method according to ISO 6222(21) or spread plate method on yeast extract agar. Legionella isolation can be conducted using the method developed by the US Center for Disease Control using buffered charcoal yeast extract agar with antibiotics.

Many other governmental agencies, cooling tower manufacturers, and industrial trade organizations have developed design and maintenance guidelines for preventing or controlling the growth of Legionella in cooling towers. However, in the US, there are no regulations requiring testing or maintaining any specified levels in these facilities.

Breeding ground

The bacteria grow best in warm water, like the kind found in hot tubs, cooling towers, hot water tanks, large plumbing systems, or parts of the air-conditioning systems of large buildings. Indoor ornamental fountains have been confirmed as a cause of Legionnaires' disease outbreaks, in which submerged lighting as a heat source was attributed to the outbreak in all documented cases. Controlling the growth of Legionella in ornamental fountains is touched on in many of the listed guidelines. However, specific guidelines for solar water heating systems http://www.wras.co.uk/PDF_Files/Preheated_Water_Report.pdfornamental fountains have also been published.

Adding an antibacterial agent to the automobiles' windshield system's reservoir is also recommended. Legionellae have been discovered in up to 40% of freshwater environments and have been in up to 80% of freshwater sites by PCR hybridization assay.

Regulations and ordinances

The guidance issued by the UK government's Health and Safety Executive (HSE) now recommends that microbiological monitoring for wet cooling systems, using a dipslide, should be performed weekly. The guidance now also recommends that routine testing for legionella bacteria in wet cooling systems be carried out at least quarterly, and more frequently when a system is being commissioned, or if the bacteria have been identified on a previous occasion.

Further non-statutory UK guidance from the Water Regulations Advisory Scheme now exists for pre-heating of water in applications such as solar water heating systems.

The City of Garland, Texas requires yearly testing for legionella bacteria at cooling towers at apartment buildings.

Malta requires twice yearly testing for Legionella bacteria at cooling towers and water fountains. Malta prohibits the installation of new cooling towers and evaporative condensers at health care facilities and schools.

The Texas Department of State Health Services has provided guidelines for hospitals to detect and prevent the spread of nosocomial infection due to legionella.