The importance of clinical surveillance in detecting legionnaires' disease outbreaks: a large outbreak in a hospital with a Legionella disinfection system-Pennsylvania, 2011-2012.
BACKGROUND
Healthcare-associated Legionnaires' disease (LD) is a preventable pneumonia with a 30% case fatality rate. The Centers for Disease Control and Prevention guidelines recommend a high index of suspicion for the diagnosis of healthcare-associated LD. We characterized an outbreak and evaluated contributing factors in a hospital using copper-silver ionization for prevention of Legionella growth in water.


METHODS
Through medical records review at a large, urban tertiary care hospital in November 2012, we identified patients diagnosed with LD during 2011-2012. Laboratory-confirmed cases were categorized as definite, probable, and not healthcare associated based on time spent in the hospital during the incubation period. We performed an environmental assessment of the hospital, including collection of samples for Legionella culture. Clinical and environmental isolates were compared by genotyping. Copper and silver ion concentrations were measured in 11 water samples.


RESULTS
We identified 5 definite and 17 probable healthcare-associated LD cases; 6 case patients died. Of 25 locations (mostly potable water) where environmental samples were obtained for Legionella-specific culture, all but 2 showed Legionella growth; 11 isolates were identical to 3 clinical isolates by sequence-based typing. Mean copper and silver concentrations were at or above the manufacturer's recommended target for Legionella control. Despite this, all samples where copper and silver concentrations were tested showed Legionella growth.


CONCLUSIONS
This outbreak was linked to the hospital's potable water system and highlights the importance of maintaining a high index of suspicion for healthcare-associated LD, even in the setting of a long-term disinfection program.
Epidemic Intelligence Service Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Alicia
A
Demirjian
Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Claressa E
CE
Lucas
Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Laurel E
LE
Garrison
Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Natalia A
NA
Kozak-Muiznieks
Pittsburgh Water and Sewer Authority.
Stanley
S
States
Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Ellen W
EW
Brown
Epidemic Intelligence Service Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Jonathan M
JM
Wortham
Epidemic Intelligence Service Pennsylvania Department of Health, Harrisburg.
Amanda
A
Beaudoin
Allegheny County Health Department.
Megan L
ML
Casey
Pennsylvania Department of Health, Pittsburgh.
Chandra
C
Marriott
Epidemic Intelligence Service VA Office of Public Health Surveillance and Research, Palo Alto, California.
Alison M
AM
Ludwig
VA Pittsburgh Healthcare System School of Medicine, University of Pittsburgh, Pennsylvania.
Ali F
AF
Sonel
VA Pittsburgh Healthcare System School of Medicine, University of Pittsburgh, Pennsylvania.
Robert R
RR
Muder
Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Lauri A
LA
Hicks
D000368:Aged; D000369:Aged, 80 and over; D003428:Cross Infection / Q000175:diagnosis / Q000453:epidemiology*; D004196:Disease Outbreaks; D004203:Disinfection / Q000379:methods*; D062665:Epidemiological Monitoring; D006801:Humans; D017053:Infection Control / Q000379:methods; D007877:Legionnaires' Disease / Q000175:diagnosis / Q000453:epidemiology*; D008875:Middle Aged; D010414:Pennsylvania / Q000453:epidemiology; D062606:Tertiary Care Centers
Legionella pneumophila; Legionnaires’ disease; disinfectants; healthcare-acquired infection; infection control