Outbreak management and implications of a nosocomial norovirus outbreak.
BACKGROUND
Noroviruses are enterically transmitted and are a frequent cause of gastroenteritis, affecting 23 million people annually in the United States. We describe a norovirus outbreak and its control in a tertiary care hospital during February-May 2004.


METHODS
Patients and health care workers met the case definition if they had new onset of vomiting and/or diarrhea during the outbreak period. Selected stool samples were tested for norovirus RNA. We also determined outbreak costs, including the estimated lost revenue associated with unit closures, sick leave, and cleaning expenses.


RESULTS
We identified 355 cases that affected 90 patients and 265 health care workers and that were clustered in the coronary care unit and psychiatry units. Attack rates were 5.3% (7 of 133) for patients and 29.9% (29 of 97) for health care workers in the coronary care unit and 16.7% (39 of 233) for patients and 38.0% (76 of 200) for health care workers in the psychiatry units. Thirteen affected health care workers (4.9%) required emergency department visits or hospitalization. Detected noroviruses had 98%-99% sequence identity with representatives of a new genogroup II.4 variant that emerged during 2002-2004 in the United States (e.g., Farmington Hills and other strains) and Europe. Aggressive infection-control measures, including closure of units and thorough disinfection using sodium hypochlorite, were required to terminate the outbreak. Costs associated with this outbreak were estimated to be $657,644.


CONCLUSIONS
The significant disruption of patient care and cost of this single nosocomial outbreak support aggressive efforts to prevent transmission of noroviruses in health care settings.
Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA. cpark@jhmi.edu
Cecilia P
CP
Johnston
Haoming
H
Qiu
John R
JR
Ticehurst
Conan
C
Dickson
Patricia
P
Rosenbaum
Patricia
P
Lawson
Amy B
AB
Stokes
Charles J
CJ
Lowenstein
Michael
M
Kaminsky
Sara E
SE
Cosgrove
Kim Y
KY
Green
Trish M
TM
Perl
D000328:Adult; D000368:Aged; D017250:Caliciviridae Infections / Q000191:economics / Q000453:epidemiology* / Q000517:prevention & control; D003428:Cross Infection / Q000191:economics / Q000453:epidemiology* / Q000821:virology; D004196:Disease Outbreaks / Q000191:economics* / Q000517:prevention & control; D005260:Female; D017048:Health Care Costs / Q000706:statistics & numerical data; D006785:Hospitals, University; D006801:Humans; D015994:Incidence; D017053:Infection Control / Q000379:methods; D017758:Infectious Disease Transmission, Patient-to-Professional; D017757:Infectious Disease Transmission, Professional-to-Patient; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D029322:Norovirus / Q000472:pathogenicity*; D010564:Personnel, Hospital