title: Outbreak of travel-related pontiac fever among hotel guests illustrating the need for better diagnostic tests.
abstract: BACKGROUND
  Pontiac fever (PF), a legionellosis with influenza-like symptoms and high attack rates, is rarely reported. Travel-related outbreaks can elude detection because infected persons are often widely removed geographically from the transmission source before illness onset. Thirty-one persons staying at an Illinois hotel during August 9 to 11, 2002, reported influenza-like symptoms to local health departments within 24 to 48 hours of checkout. We investigated to identify the cause and source of illness to guide control measures.
  
  
  METHODS
  Hotel water samples were collected for culture. A telephone questionnaire detailing illness symptoms and exposures was administered to all who were guests at the hotel from August 9 to 15 (n = 380). A case was defined as onset of fever, headache, and myalgia in a guest in the 14 days following the hotel stay. Patient sera were tested by hemagglutination assay for antibodies to Legionella species.
  
  
  RESULTS
  Among 204 questionnaire respondents from 15 states and Canada, 50 met the case definition. Among persons exposed to the swimming pool/whirlpool spa area, 63% (47 of 75) became ill versus 3% (3 of 110) of unexposed persons (relative risk 23.0, 95% CI 7.4-71.1). Illness risk increased with increasing time exposed to the pool/spa. Approximately 95 to 115 bathers per day, two to three times above the usual number, used the spa during August 9 to 11. Three Legionella species, L. dumoffii, L. maceachernii, and L. micdadei, were isolated from spa filter backwash cultures. Two of 15 ill persons with acute- and convalescent-phase sera had a greater than fourfold rise in antibody titer to L. micdadei.
  
  
  CONCLUSIONS
  PF was associated with exposure to a hotel pool/spa area. Heavy bather usage likely contributed to a decreased effectiveness of the disinfectant in the whirlpool spa, possibly promoting bacterial aerosolization. Linking case information from many states is essential in identifying and eliminating the source of disease transmission in travel-related outbreaks of PF. Clinicians should be aware of PF in the differential diagnosis of patients with influenza-like symptoms following recent travel, particularly with exposure to a communal-use whirlpool spa.
authors.affiliation: Illinois Department of Public Health, Chicago, IL, USA.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Huhn
authors.forename: Barb
authors.initials: B
authors.lastname: Adam
authors.forename: Roger
authors.initials: R
authors.lastname: Ruden
authors.forename: Lisa
authors.initials: L
authors.lastname: Hilliard
authors.forename: Pam
authors.initials: P
authors.lastname: Kirkpatrick
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Todd
authors.forename: William
authors.initials: W
authors.lastname: Crafts
authors.forename: Douglas
authors.initials: D
authors.lastname: Passaro
authors.forename: Mark S
authors.initials: MS
authors.lastname: Dworkin
mesh_terms: D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007087:Illinois / Q000453:epidemiology; D007875:Legionella / Q000145:classification / Q000276:immunology / Q000302:isolation & purification; D007876:Legionellosis / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011795:Surveys and Questionnaires; D013551:Swimming Pools; D014195:Travel; D014871:Water Microbiology
chemical_list: D000907:Antibodies, Bacterial