Legionellosis historical perspective

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ogechukwu Hannah Nnabude, MD Tarek Nafee, M.D. [2]

Legionnaires' disease acquired its name in 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in Philadelphia. On January 18, 1977 the causative agent was identified as a previously unknown bacterium, subsequently named Legionella. There have been numerous outbreaks of Legionnaires since it was first discovered. Some of the outbreaks of Legionella are listed below in chronological order.

The first recognized Legionella outbreak occurred in 1976 during a meeting of the American Legion in Philadelphia, Pennsylvania. About 29 of the 182 people that contracted the infection died ^[1]. It was after the bacterium had been successfully isolated that previous cases of Legionella were identified.

In 1985, Stafford District General Hospital experienced a Legionella outbreak. A total of 68 confirmed cases were treated in hospital and 22 of these patients died. A further 35 patients were suspected cases of Legionnaires' disease, 14 of whom only required treatment at home. Legionella was found in the water within the cooling tower and a chiller unit which cooled the air entering the outpatient department. The chiller unit is believed to be the major source of the outbreak ^[2].

During a flower exhibition in Bovenkarspel, Netherlands, an outbreak of Legionella occurred. It is believed to have been caused by a contamination of the whirlpools in halls 3 and 4, and the sprinkler in hall 8, all of which tested culture positive for Legionella. There were 133 confirmed cases and 55 possible cases out of the 77061 visitors to the exhibition ^[3].

In Murcia, Spain, over 800 suspected cases of Legionnaires' disease were recorded. Of these cases, 449 were confirmed to be caused by Legionella. This is currently the largest outbreak of Legionella ever recorded. About 1% of affected patients died from the disease ^[4].

The first recognized outbreak of Legionella in Norway was in 2001 when 28 people were infected in the city of Stavanger, and seven died. Of the 28 patients, 21 were within the city of Stavanger, five were in other areas in Norway, and two were from other countries, with one being in England and the other in Germany. This was initially a mystery to the investigators. However, it was discovered that a cooling unit from a nearby hotel was the source of the infection. The air outlet was found to be just over 16 feet above the ground and located close to a bus station. This was determined source of contact for the patient in Germany and the patient in England ^[5]

In 2002, six women and one man in Barrow-In-Furness died as a result of the illness, another 172 people also contracted the disease. The outbreak was traced to a contaminated cooling tower at the town’s Forum 28 arts center.

Between November 2003 and January 2004, an outbreak of Legionnaires' disease occurred in Pas-de-Calais, France. There were 18 fatalities out of the 86 laboratory-confirmed cases, giving the outbreak a mortality rate of about 21%. A Legionella pneumophila strain named Lens was isolated from samples of air, wastewater, and cooling towers from plant A. Researchers determined that the dispersion extended over a distance of at least 6 km (3.75 miles) from the plant. ^[6]

In May 2005 there was another outbreak of Legionnaires' disease in Norway, in the town of Fredrikstad. Initially, 56 patients were confirmed infected and ten people were dead. However, on serological testing of other patients with community acquired pneumonia, another 47 patients were discovered to have the disease, bringing the total for the oubreak to at least 103, 16 of whom are probable cases. The source of the outbreak unexpectedly came from an air scrubber that disseminated that bacterium over a distance of about 10 km (6.25 miles). ^{[7] [8]}

In mid-2005, Christchurch, New Zealand experienced an outbreak of Legionnaires' disease. There were 3 deaths out of the 19 confirmed cases. Legionella pneumophila serogroup 1 (Lpsg1) was identified as the causative agent for all cases. A water cooling tower located in the center of the clusters is believed to be the source of the outbreak^[9].

An outbreak of Legionnaires' disease at the Seven Oaks Home for the Aged, a nursing home in Toronto, in the province of Ontario, Canada from September to October 2005 resulted in illness in 135 people, 23 (17%) of whom died. Researchers confirmed that a contaminated air conditioning cooling tower was the source of the outbreak. ^[10]

An outbreak linked to contaminated water in an industrial cooling tower caused 181 confirmed cases, 14 of which resulted in death ^[11].

In 2012, 50 confirmed cases and 49 suspected cases of Legionella occurred in Edinburg, Scotland. It led to the death of 4 people. Cooling towers in the affected area are suspected to be the cause of the outbreak. ^[12]

A widespread outbreak in the Vila Franca de Xira district infected 377 people, and caused the death of 14. A combination of factors led to the outbreak becoming widespread including temperatures that were unusually high for that time of the year, leading to increased proliferation of Legionella in the cooling tower to which the outbreak was traced, and the high humidity that is believed to increase the spread of Legionella ^{[13] [14]}.

Whirlpool spas at a state fair were linked to a Legionella outbreak in Fletcher, North Carolina, United States that claimed the lives of 4 out of the 136 confirmed cases people infected. ^[15]

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