Epidemiologic Notes and Reports
Outbreak of Yersinia enterocolitica -- Washington State
In December 1981 and January 1982, an outbreak of predominantly
gastroenteritis caused by Yersinia enterocolitica occurred among 87
persons in Washington state. The illness was associated with the
ingestion of a locally produced brand of tofu, an oriental soybean
curd, packed in untreated spring water. It was sold primarily in
western Washington with limited distribution in Alaska, Idaho, and
Oregon. Y. enterocolitica was isolated from the tofu, the
processing
plant's water supply, and several sites within the plant.
In mid-January 1982, the Seattle-King County Health Department
received reports from two hospital laboratories of 12 positive
stool
cultures of Y. enterocolitica associated with gastrointestinal
illness; during the previous year, 10 Y. enterocolitica isolates
were
reported in the entire county. Increased surveillance by
Seattle-King
County and the Washington State Department of Social and Health
Services over several months identified additional cases, for a
total
of 87. A case was defined as anyone who was culture-positive
and/or
who had had contact with a case and had fever in conjunction with
diarrhea or abdominal cramps.
Of the 87 cases, 56 were culture-positive; 38 patients had
enteritis, six had only extra-intestinal infections, four had both
extra-intestinal infections and enteritis, and eight were
asymptomatic
carriers. The 10 cases of extra-intestinal infection included
patients with wound ulcers (two), inguinal lymphadenopathy (two,
one
with a perineal ulcer), pneumonia (two), labial infection (one),
arthritis (one), septicemia (one), and pharyngitis (one). Nine
(16.1%) of the 56 culture-positive patients were 1 year of age, 12
(21.4%) were 1 to 4 years old, 7 (12.5%) were 5 to 18 years old,
and
28 (50.0%) were
18 years old. Among 38 culture-positive cases with
enteritis, who tended to have more severe illness and on whom more
complete information was available, the following were reported:
fever
(91%), abdominal pain (81%), diarrhea (76%), nausea (54%), vomiting
(39%), bloody stools (27%), joint pain (42%), and skin rash (43%).
Symptoms lasted from 1 day to 4 weeks (mean 10 days). Two
patients,
however, were ill for over 2 months. Seventeen patients were
hospitalized for from 2 to 11 days (average 9.7 days); two of those
hospitalized had appendectomies and one, a partial colectomy. One
patient was also culture-positive for Salmonella typhimurium and
one
for rotavirus, as well as for Y. enterocolitica.
A neighborhood case-control study of 11 ill persons and 11
controls revealed an association between Y. enterocolitica
infection
and tofu consumption (p 0.01). Questions regarding animal
contacts,
water sources, raw milk consumption, travel, and day-care settings,
as
well as extensive food histories, did not identify any other common
sources. Further investigation revealed that 70 (80.5%) of the 87
persons interviewed had consumed the same brand of tofu within the
2
weeks before onset of symptoms. For five culture-positive persons
who
had consumed only one meal of tofu, the incubation period averaged
6.6
days (range 4-11 days).
The tofu plant in King County is located on a rural island in
Puget Sound. The plant water supply, which originates from a
spring
approximately 0.5 mile from the plant, is shared by four residences
and an apple-cider plant. No illness was reported among consumers
of
the cider. Inspection of the tofu plant on January 20, 1982,
disclosed unsanitary conditions, including poor personal hygiene,
use
of an outdoor privy, and unsanitary equipment. Samples of tofu and
the plant water supply were positive for Y. enterocolitica, as were
stool specimens collected from two of 12 employees; both employees
were asymptomatic.
A voluntary recall of the product was instituted from January
21
to January 25. Further sampling and laboratory analysis of the
tofu
demonstrated high fecal-coliform counts. Production was resumed
after
a water-purification system was installed. Laboratory results of
plasmid analysis, determination of enterotoxin production, and
serotyping are pending.
Reported by C Nolan, MD, N Harris, DVM, Seattle-King County Health
Dept, J Ballard, MS, J Allard, PhD, J Kobayashi, MD, State
Epidemiologist, Washington State Dept of Social and Health Svcs.
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