title: An outbreak of legionnaires disease caused by long-distance spread from an industrial air scrubber in Sarpsborg, Norway.
abstract: BACKGROUND
  On 21 May 2005, the Norwegian health authorities were alerted by officials from a local hospital that several recent patients had received the diagnosis of legionnaires disease; all patients resided in 2 neighboring municipalities. We investigated the outbreak to identify the source and to implement control measures.
  
  
  METHODS
  We interviewed all surviving case patients and investigated and harvested samples from 23 businesses with cooling towers and other potential infection sources. The locations of the businesses and the patients' residences and movements were mapped. We calculated attack rates and risk ratios among people living within various radii of each potential source. Isolates of Legionella pneumophila were compared using molecular methods.
  
  
  RESULTS
  Among 56 case patients, 10 died. The case patients became ill 12-25 May, resided up to 20 km apart, and had not visited places in common. Those living up to 1 km from a particular air scrubber had the highest risk ratio, and only for this source did the risk ratio decrease as the radius widened. Genetically identical L. pneumophila serogroup 1 isolates were recovered from patients and the air scrubber. The air scrubber is an industrial pollution-control device that cleans air for dust particles by spraying with water. The circulating water had a high organic content, pH of 8-9, and temperature of 40 degrees C. The air was expelled at 20 m/s and contained a high amount of aerosolized water.
  
  
  CONCLUSIONS
  The high velocity, large drift, and high humidity in the air scrubber may have contributed to the wide spread of Legionella species, probably for >10 km. The risk of Legionella spread from air scrubbers should be assessed.
authors.affiliation: Norwegian Institute of Public Health, Oslo, Norway. karin.nygard@fhi.no
authors.forename: Karin
authors.initials: K
authors.lastname: Nygård
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Werner-Johansen
authors.forename: Svein
authors.initials: S
authors.lastname: Rønsen
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Caugant
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Simonsen
authors.forename: Anita
authors.initials: A
authors.lastname: Kanestrøm
authors.forename: Eirik
authors.initials: E
authors.lastname: Ask
authors.forename: Jetmund
authors.initials: J
authors.lastname: Ringstad
authors.forename: Rune
authors.initials: R
authors.lastname: Ødegård
authors.forename: Tore
authors.initials: T
authors.lastname: Jensen
authors.forename: Truls
authors.initials: T
authors.lastname: Krogh
authors.forename: E Arne
authors.initials: EA
authors.lastname: Høiby
authors.forename: Eivind
authors.initials: E
authors.lastname: Ragnhildstveit
authors.forename: Ingeborg S
authors.initials: IS
authors.lastname: Aaberge
authors.forename: Preben
authors.initials: P
authors.lastname: Aavitsland
mesh_terms: D000328:Adult; D000336:Aerosols / Q000737:chemistry; D000368:Aged; D000369:Aged, 80 and over; D000389:Air Conditioning; D000391:Air Microbiology; D015331:Cohort Studies; D004196:Disease Outbreaks; D004866:Equipment Contamination; D005260:Female; D006801:Humans; D016952:Legionella pneumophila / Q000302:isolation & purification*; D007877:Legionnaires' Disease / Q000453:epidemiology* / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D012189:Retrospective Studies; D014871:Water Microbiology
chemical_list: D000336:Aerosols