A prolonged outbreak of Escherichia coli O157:H7 infections caused by commercially distributed raw milk.
A protracted outbreak of Escherichia coli O157:H7 infections was caused by consumption of unpasteurized ("raw") milk sold at Oregon grocery stores. Although it never caused a noticeable increase in reported infections, the outbreak was recognized because of routine follow-up interviews. Six of 16 Portland-area cases reported between December 1992 and April 1993 involved people who drank raw milk from dairy A. By pulsed-field gel electrophoresis (PFGE), E. coli O157:H7 isolates from these cases and from the dairy A herd were homologous (initially, 4 of 132 animals were E. coli O157:H7-positive). Despite public warnings, new labeling requirements, and increased monitoring of dairy A, retail sales and dairy-associated infections continued until June 1994 (a total of 14 primary cases). Seven distinguishable PFGE patterns in 3 homology groups were identified among patient and dairy herd E. coli O157:H7 isolates. Without restrictions on distribution, E. coli O157:H7 outbreaks caused by raw milk consumption can continue indefinitely, with infections occurring intermittently and unpredictably.
Keene
W E
WE
Acute and Communicable Disease Section, Oregon Health Division, Portland 97232, USA. keene@ohsu.edu
Hedberg
K
K
Herriott
D E
DE
Hancock
D D
DD
McKay
R W
RW
Barrett
T J
TJ
Fleming
D W
DW
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002417:Cattle; D002648:Child; D002675:Child, Preschool; D003967:Diarrhea / Q000453:epidemiology / Q000209:etiology; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000209:etiology / Q000382:microbiology; D019453:Escherichia coli O157 / Q000145:classification / Q000302:isolation & purification; D005500:Follow-Up Studies; D005516:Food Microbiology; D006801:Humans; D007223:Infant; D008875:Middle Aged; D008892:Milk / Q000382:microbiology*; D009922:Oregon / Q000453:epidemiology; D013997:Time Factors