An outbreak of Escherichia coli O157:H7 infections among visitors to a dairy farm.
BACKGROUND
Outbreaks of Escherichia coli O157:H7 infections have involved direct transmission from animals and their environment to humans. We describe an outbreak among visitors to a Pennsylvania dairy and petting farm that provides public access to animals.


METHODS
We conducted both a case-control study among visitors to a farm to identify risk factors for infection and a household survey to determine the rates of diarrheal illness among these visitors. We performed an extensive environmental study to identify sources of E. coli O157:H7 on the farm.


RESULTS
Fifty-one patients with confirmed or suspected E. coli O157:H7 infection were enrolled in the case-control study. The median age of the patients was four years, and the hemolytic-uremic syndrome developed in eight. Contact with calves and their environment was associated with an increased risk of infection, whereas hand washing was protective. The household survey indicated that visitors to the farm during the outbreak had higher than expected rates of diarrhea. Environmental studies showed that 28 of the 216 cattle on the farm (13 percent) were colonized with E. coli O157:H7 that had the same distinct pattern on pulsed-field gel electrophoresis that was found in isolates from the patients. This organism was also recovered from surfaces that were accessible to the public.


CONCLUSIONS
In a large outbreak of E. coli O157:H7 infections among visitors to a dairy farm, predominantly children, high rates of carriage of E. coli O157:H7 among calves and young cattle most likely resulted in contamination of both the animals' hides and the environment.
Crump
John A
JA
Epidemic Intelligence Service, Division of Applied Public Health Training, Epidemiology Program Office, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta 30333, USA. jcrump@cdc.gov
Sulka
Alana C
AC
Langer
Adam J
AJ
Schaben
Chad
C
Crielly
Anita S
AS
Gage
Robert
R
Baysinger
Michael
M
Moll
Maria
M
Withers
Gisela
G
Toney
Denise M
DM
Hunter
Susan B
SB
Hoekstra
R Michael
RM
Wong
Stephanie K
SK
Griffin
Patricia M
PM
Van Gilder
Thomas J
TJ
D000293:Adolescent; D000328:Adult; D000818:Animals; D018441:Biofilms; D016022:Case-Control Studies; D002417:Cattle / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D003612:Dairying; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000635:transmission*; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005260:Female; D006306:Health Surveys; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010414:Pennsylvania / Q000453:epidemiology; D012307:Risk Factors