A large, travel-associated outbreak of legionellosis among hotel guests: utility of the urine antigen assay in confirming Pontiac fever.
BACKGROUND
During March 2004, a large outbreak of legionnaires disease and Pontiac fever occurred among hotel guests in Oklahoma. An investigation was conducted to identify the source and evaluate the utility of the Legionella urine antigen assay and serologic testing for the identification of Pontiac fever.


METHODS
A retrospective cohort investigation of hotel guests and employees and an environmental evaluation were performed. Participants were interviewed, and clinical specimens were collected from consenting individuals.


RESULTS
Six cases of legionnaires disease and 101 cases of Pontiac fever were identified. Exposure to the indoor pool and hot tub area was associated with legionellosis (relative risk, 4.4; 95% confidence interval, 2.8-6.9). Specimens from the pool and hot tub tested positive for Legionella pneumophila serogroup 1 by polymerase chain reaction. For Pontiac fever, the sensitivity and positive predictive value were 35.7% and 100%, respectively, for the urine antigen assay, and 46.4% and 90%, respectively, for serologic testing. The specificity and negative predictive value were 100% and 47.8%, respectively, for the urine antigen assay, and 89.3% and 45.5%, respectively, for serologic testing.


CONCLUSIONS
Urine antigen testing, with or without serologic testing, can be used to confirm outbreak-associated cases of Pontiac fever caused by L. pneumophila serogroup 1.
Burnsed
Laurence J
LJ
Communicable Disease Div., Oklahoma State Department of Health, Oklahoma City, OK 73117-1299, USA. laurence@health.ok.gov
Hicks
Lauri A
LA
Smithee
Laura M K
LM
Fields
Barry S
BS
Bradley
Kristy K
KK
Pascoe
Neil
N
Richards
Shawn M
SM
Mallonee
Sue
S
Littrell
Lisa
L
Benson
Robert F
RF
Moore
Matthew R
MR
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000652:urine*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007223:Infant; D007877:Legionnaires' Disease / Q000175:diagnosis* / Q000453:epidemiology* / Q000276:immunology / Q000652:urine; D008297:Male; D008875:Middle Aged; D009825:Oklahoma / Q000453:epidemiology; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D014195:Travel
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial