title: Lessons From an Outbreak of Legionnaires' Disease on a Hematology-Oncology Unit.
abstract: OBJECTIVES To define the scope of an outbreak of Legionnaires' disease (LD), to identify the source, and to stop transmission. DESIGN AND SETTING Epidemiologic investigation of an LD outbreak among patients and a visitor exposed to a newly constructed hematology-oncology unit. METHODS An LD case was defined as radiographically confirmed pneumonia in a person with positive urinary antigen testing and/or respiratory culture for Legionella and exposure to the hematology-oncology unit after February 20, 2014. Cases were classified as definitely or probably healthcare-associated based on whether they were exposed to the unit for all or part of the incubation period (2-10 days). We conducted an environmental assessment and collected water samples for culture. Clinical and environmental isolates were compared by monoclonal antibody (MAb) and sequence-based typing. RESULTS Over a 12-week period, 10 cases were identified, including 6 definite and 4 probable cases. Environmental sampling revealed Legionella pneumophila serogroup 1 (Lp1) in the potable water at 9 of 10 unit sites (90%), including all patient rooms tested. The 3 clinical isolates were identical to environmental isolates from the unit (MAb2-positive, sequence type ST36). No cases occurred with exposure after the implementation of water restrictions followed by point-of-use filters. CONCLUSIONS Contamination of the unit's potable water system with Lp1 strain ST36 was the likely source of this outbreak. Healthcare providers should routinely test patients who develop pneumonia at least 2 days after hospital admission for LD. A single case of LD that is definitely healthcare associated should prompt a full investigation. Infect Control Hosp Epidemiol 2017;38:306-313.
authors.affiliation: 1Epidemic Intelligence Service Program,Atlanta,Georgia.
authors.forename: Louise K
authors.initials: LK
authors.lastname: Francois Watkins
authors.affiliation: 2Centers for Disease Control and Prevention,Atlanta,Georgia.
authors.forename: Karrie-Ann E
authors.initials: KE
authors.lastname: Toews
authors.affiliation: 2Centers for Disease Control and Prevention,Atlanta,Georgia.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Harris
authors.affiliation: 3Alabama Department of Public Health,Montgomery,Alabama.
authors.forename: Sherri
authors.initials: S
authors.lastname: Davidson
authors.affiliation: 4Jefferson County Department of Health,Birmingham,Alabama.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Ayers-Millsap
authors.affiliation: 2Centers for Disease Control and Prevention,Atlanta,Georgia.
authors.forename: Claressa E
authors.initials: CE
authors.lastname: Lucas
authors.affiliation: 2Centers for Disease Control and Prevention,Atlanta,Georgia.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Hubbard
authors.affiliation: 2Centers for Disease Control and Prevention,Atlanta,Georgia.
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Kozak-Muiznieks
authors.affiliation: 4Jefferson County Department of Health,Birmingham,Alabama.
authors.forename: Edward
authors.initials: E
authors.lastname: Khan
authors.affiliation: 2Centers for Disease Control and Prevention,Atlanta,Georgia.
authors.forename: Preeta K
authors.initials: PK
authors.lastname: Kutty
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000407:Alabama; D003428:Cross Infection / Q000209:etiology* / Q000382:microbiology; D004196:Disease Outbreaks; D060766:Drinking Water / Q000382:microbiology*; D005260:Female; D006405:Hematology; D006801:Humans; D016952:Legionella pneumophila / Q000145:classification / Q000302:isolation & purification; D007877:Legionnaires' Disease / Q000175:diagnosis* / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D016522:Oncology Service, Hospital; D014871:Water Microbiology
chemical_list: D060766:Drinking Water