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Epidemiologic Notes and Reports Chronic Diarrhea Associated with Raw Milk Consumption -- Minnesota

On July 10, 1984, the Minnesota Department of Health was informed by Brainerd, Minnesota, physicians that 20-50 patients in that area had experienced onset of chronic diarrhea since January 1984; they were unaware of any patients who had recovered. Initial investigation by the Minnesota Department of Health identified 23 persons who met the case definition of acute onset of diarrhea, lasting at least 4 weeks, in a person with no underlying illness known to cause chronic diarrhea. A case-control study of these case-patients and 46 gender- and age-matched neighborhood controls revealed that illness was strongly associated with drinking raw milk from a local dairy (p 0.1 x 10))-5))); no other risk factors were identified, and the dairy voluntarily stopped selling raw milk. Based on a study of 94 families (394 persons) who were regular customers of the dairy, the attack rate for chronic diarrhea with onset between November 1, 1983, and September 1, 1984, was 8%. All age groups were affected, but the attack rate was lowest for children (3%) and highest for adults 61-80 years of age (23%).

A review of medical records for patients hospitalized with diarrhea at the community hospital since January 1982 and interviews of regular and occasional customers of the dairy identified 122 outbreak-related case-patients. The first case-patient had onset of illness in December 1983 with onsets continuing through July 1984 (Figure 3). All case-patients had consumed raw milk from the implicated dairy during the 3 weeks before onsets of illness. To date there is no evidence of person-to-person transmission of illness. Illness was characterized by acute onset of watery diarrhea (frequently 10-20 stools per day) often associated with marked urgency that greatly limited patients' activities. Over 50% of the case-patients also experienced abdominal cramping. Nausea, vomiting, and/or systemic symptoms occurred infrequently. Seven patients who drank raw milk only on 1 day or 2 consecutive days had onsets of illness 4-23 days after exposure (median 15 days). Although many patients have noted gradual improvement in the frequency of diarrheal episodes, only 11 (9%) have fully recovered. Twenty-two patients have received empiric therapy with at least one antimicrobial agent for at least 7 days. Metronidazole (14 patients), erythromycin (eight), tetracycline (two), trimethoprim/sulfamethoxazole (two), and cephalexin (one) were used; no one responded to treatment. Continuing microbiologic and toxicologic studies performed at CDC of clinical specimens, raw milk samples, and environmental samples from this dairy have not yielded any known enteric pathogens or toxins. Reported by Acute Disease Epidemiology Section, Minnesota Dept of Health; Enteric Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial note: The etiologic agent of this illness has not yet been identified, but available data suggest an infectious etiology. Raw milk was implicated as the vehicle of transmission in this outbreak. However, as with other enteric pathogens, such as Salmonella sp., and Campylobacter jejuni, for which raw milk is an important vehicle, other as yet unidentified vehicles may also be associated with this illness. To aid in further understanding this syndrome, outbreaks of diarrheal illness similar to that reported here should be reported to CDC through local and state health departments.

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