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Source: Legionellosis outbreak at a flower show. ProMED-mail; April 5, 1999; http://www.healthnet.org/programs/program.html.
This report describes an outbreak of at least 231 cases of Legionnaire’s disease following a flower show in Bovenkarspel, The Netherlands, which attracted up to 12,000 people per day during the last week of February. Twenty-one people have died to date. Preliminary studies suggest that the organism was spread by a warm-water whirlpool spa in the consumer products show, which was held concurrently with the flower show, and which attracted another 80,000 people. A water sample from the spa was positive for Legionella by PCR assay, although cultures were negative.
Epidemiological studies of a cohort of people who attended the exhibit, as well as all 1500 employees, are ongoing. Since this outbreak, Legionella has been isolated in a second spa in The Netherlands, prompting notification of the 40 or more people who had recently used the jet massage equipment.
A similar outbreak of Legionella anisa infection occurred in San Jose, Cali., in 1988 among 34 of 56 people attending a conference in a local hotel.1 L. anisa was isolated from a decorative fountain in the hotel lobby where a luncheon had been set up for the conference attendees. In contrast to the outbreak described above, most of the victims experienced an acute febrile respiratory illness with fairly rapid resolution of symptoms, usually within five days of onset—otherwise known as Pontiac fever. The attack rate was high (82%) and rapid in onset (within 56 hours). Serological studies of hotel employees found positive antibody titers to L. anisa in 42%.
Investigations of the San Jose outbreak revealed no set schedule for fountain maintenance, which used recirculated water with no disinfecting chemicals. The fountain was cleaned by mopping the tile floor with municipal hot water and running it through the jets, which permitted persistence of the organism. In contrast to the ongoing outbreak in The Netherlands, L. anisa infection does not progress to pneumonia and has not been associated with death.
Legionella infection has been transmitted in other settings during demonstrations of new hot tub and spa equipment when chlorination is often disregarded because the equipment is being used solely for demonstration purposes. The deadly outbreak in The Netherlands should serve as a severe reminder that disinfection protocols are necessary for all spas, fountains, and misting devices used in public places.
1. Fenstersheib MD, et al. Outbreak of Pontiac fever due to Legionella anisa. Lancet 1990;336:35-37.