The bacterium first hit the headlines in 1976 following an outbreak at the American Legion Convention in Philadelphia where 182 people suffered an acute respiratory disease, 29 of whom died. Subsequent investigations identified the legionella bacterium which was, at that time, new to science.
A review of stored pathology samples revealed that undiagnosed cases had occurred at least as far back as 1947. UK-based outbreaks of the disease were identified at Kingston in 1980 and Glasgow in 1984. But it was the Stafford hospital outbreak in 1985, followed by the BBC outbreak in 1988, the Corby outbreak in 1996 and more recently the Barrow outbreak in August 2002 that really raised the profile of the disease.
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Philadelphia, 1976 : The first recognized outbreak occurred on July 27, 1976 at the Bellevue Stratford Hotel in Philadelphia, Pennsylvania, where members of the American Legion, a United States military veterans association, had gathered for the American Bicentennial. Within two days of the event’s start, veterans began falling ill with a then-unidentified pneumonia. Numbers differ, but perhaps as many as 221 persons were given medical treatment; 34 died. At the time, the U.S. was debating the risk of a possible swine flu epidemic, and this incident prompted the passage of a national swine flu vaccination program. That cause was ruled out, and research continued for months, with various theories discussed in scientific and mass media that ranged from toxic chemicals to terrorism (domestic or foreign) aimed at the veterans. The U.S. Centers for Disease Control and Prevention mounted an unprecedented investigation. By September, the focus had shifted from outside causes such as a disease carrier to the hotel environment itself. In January 1977, the Legionellosis bacterium was finally identified and isolated, and found to be breeding in the cooling tower of the hotel’s air conditioning system, which then spread it through the entire building. This finding prompted new regulations worldwide for climate control systems.
Some do not believe that the air conditioning was conclusively proven to be the cause of the outbreak. According to Dr. Victor L. Yu, chief of the infectious disease section at the Oakland Veterans Affairs Medical Center in Pittsburgh, researchers still haven’t identified the exact source. Morbidity and Mortality Weekly Report (MMWR), a weekly publication of the US Centers for Disease Control and Prevention (CDC), stated in 1977 that no source was found in this first outbreak of Legionnaires’ disease at the Bellevue Stratford Hotel.
Netherlands, 1999: In March 1999, an outbreak in the Netherlands occurred during a flower exhibition in Bovenkarspel. 200 people became ill and at least 32 people died. Probably more people died from it, but these were buried before the Legionella infection was recognized. The source of the bacteria were probably a whirlpool and a moisturizer in the exhibition area.
Spain, 2001: The world’s largest outbreak of Legionnaires’ disease happened in July 2001 (the patients began to go to the hospital on July 7), in Murcia, Spain, where more than 800 suspected cases were recorded by July 22, when the last case was treated; 636-696 of these cases were estimated and 449 confirmed (so, at least 16,000 persons were exposed to the bacterium) and 6 died (this is a case-fatality rate of approximately 1 percent).
A controlled case study matching 85 patients living outside the city of Murcia with two controls each was undertaken to identify the outbreak source; the epidemiologic investigation implicated the cooling towers at a city hospital (Morales Meseguer Hospital). An environmental isolate from these towers with an identical molecular pattern as the clinical isolates was subsequently identified and supported that epidemiologic conclusion.
Norway, 2001: The first known case of the disease in Norway occurred in 2001 when 28 people were infected in the city of Stavanger, and seven died. At first the authorities were puzzled as several of the victims lived in other locations, including one in Germany and another in England. After a massive investigation a fountain in the small lake of Breiavatnet was suspected as the source of the outbreak. But the fountain had not sprayed the bacteria into the air, the source was a cooling tower at the nearby SAS Radisson hotel. Only three of the infected had stayed at the hotel, but the exit vent of the cooling tower was at ground level next to a public bus stop, explaining the other victims.
United Kingdom, 2002: In 2002, Barrow-in-Furness suffered the U.K.’s worst 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.
France, 2004: Researchers found that the Legionnaires’ disease bacteria spread through the air up to 6 kilometers from a large contaminated cooling tower at a petrochemical plant in Pas-de-Calais in northern France. That outbreak killed 21 of the 86 people with laboratory-confirmed infection.
Norway, 2005: In May 2005 there was a second greater outbreak in Norway, this time originating in the southeastern town of Fredrikstad. As of 8 June 2005, 52 patients were confirmed infected and ten people were dead. The dead were all from Fredrikstad or nearby cities, in age ranging from 68 to early 90's. The source of the outbreak unexpectedly came from an air scrubber (an industrial air purification facility; this particular one operated by Borregaard Industries in Sarpsborg). Such an installation has never before been reported as a source of Legionellosis anywhere in the world. Although the source was finally identified by DNA matching, it was also fairly well identified by analysing risk increases from people living near suspected sources.
Toronto, 2005: In October 2005 at least 21 people died and over 100 fell ill during an outbreak at the Seven Oaks Home for the Aged in Toronto, Ontario, Canada. Legionnaire’s disease was originally ruled out as being the cause, but post-mortem examinations confirmed that victims had Legionella bacteria in their lungs. The outbreak is still being investigated, and researchers believe this particular outbreak may be related to a new strain of the bacteria.