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Food-borne Hepatitis A -- Oklahoma, Texas
Two unrelated outbreaks of hepatitis A, involving a total of 326 people, occurred in Oklahoma and Texas during September and October 1983. Both were associated with restaurant food.
Oklahoma: The first outbreak occurred in Marietta in Love County (county population approximately 7,800), where 203 persons became ill from August 15 to October 10 (Figure 3). Hepatitis A was defined as: (1) jaundice or (2) serum glutamic oxalacetic transaminase enzyme (SGOT) greater than 100 mIU/ml plus nausea, vomiting, or fever or (3) a positive serum anti-hepatitis A virus (HAV) immunoglobulin (IgM). Twelve outbreak-related cases were reported elsewhere--10 in Texas and two in California. Patients ranged in age from 2 to 66 years (median 22 years); 52% were male.
Of 175 patients interviewed about exposures, 161 (92%) had eaten at a drive-in restaurant 2-6 weeks before onset of illness. Twenty-nine patients were employed as foodhandlers at eight other restaurants in town. Two worked on icing and cream-filling machines at a local bakery that distributed cookies nationwide.
The index patient, a 22-year-old foodhandler at the drive-in restaurant, developed jaundice on August 19. Investigation into his personal hygiene suggested that his handwashing practices were good, although he developed diarrhea on August 15 and continued to work up to the onset of his jaundice.
To identify risk factors of the outbreak, a survey was conducted of local high-school students. Twenty-two (13%) of 169 students who completed questionnaires had hepatitis A. The only exposure associated with illness was eating at the same drive-in restaurant during August. Twenty-one (19%) of 110 students who had eaten there became ill, compared with one (2%) of 59 who had not eaten at the restaurant (p 0.01). Attack rates increased with the number of meals eaten. No single food or drink could be implicated as a vehicle for transmission.
Most of the town's foodhandlers either had been exposed at the drive-in restaurant or were coworkers of infected foodhandlers; therefore, on September 16, the Oklahoma State Health Department recommended that immune globulin (IG) be given to patrons of five restaurants in Marietta where ill foodhandlers had prepared uncooked foods and to all foodhandlers who worked in the town. A total of 5,500 doses were given. The drive-in restaurant voluntarily closed for a month; in addition, following a U.S. Food and Drug Administration investigation, the bakery, at which two hepatitis A patients worked, voluntarily recalled selected products. No additional cases have been reported.
Texas: The second outbreak occurred in Lubbock, a city of 180,000 people. From October 5, through October 28, 1983, 123 physician-diagnosed cases of hepatitis A were reported to the Lubbock City Health Department. One hundred of these patients had eaten at a salad bar-type restaurant in the city 14-60 days before illness (Figure 4). Eight of the patients, including three cooks, were employed at the restaurant. Patients with restaurant-associated hepatitis A ranged in age from 7 to 64 years (mean 31 years); 65% were male; and 92% became jaundiced.
A case-control study was performed using 50 patients and 59 controls who had eaten at the restaurant only once between August 24 and September 17; controls had eaten with the patients and had sera negative for anti-HAV. Eating lettuce, tomatoes, or pickles on sandwiches was strongly associated with illness (p 0.001); eating these vegetables at the salad bar, which was prepared by different foodhandlers, was not.
Eighty-seven of the restaurant's 96 employees, including all the cooks, completed questionnaires and underwent screening for anti-HAV immunoglobulin G (IgG) and IgM. One sandwich-maker experienced nausea and vomiting in mid-September but was never jaundiced. Two of his household members contracted hepatitis A during the outbreak, despite never having eaten at the restaurant, and only he made the implicated sandwiches during periods when patients were known to have been exposed. An anti-HAV IgM drawn on November 2 was negative; however, an anti-HAV IgG was positive.
On October 8, the Lubbock City Health Department advised that the following persons receive immune globulin (IG) as prophylaxis against hepatitis A: (1) all employees of the restaurant, (2) anyone who had eaten at the restaurant during the previous 2 weeks, and (3) all household contacts of persons with hepatitis A. Patrons were included because of the possibility of continuing food contamination by frequent sewage backups in the restaurant's kitchen. During October 1983, an estimated 15,000-20,000 doses of IG were given in the Lubbock area, mostly by private physicians. Reported by M Gaither, JP Lofgren, MD, State Epidemiologist, Arkansas State Dept of Health; G Empey, Kern County Health Dept, AF Taylor, MPH, TG Stephenson, MPH, GA Pettersen, MD, San Bernadino Dept of Public Health, J Chin, MD, State Epidemiologist, California Dept of Health Svcs; B Baylor, MD, G Gwin, P Hunt, JT O'Connor, DO, V Smith, DO, Love County Health Center, W Baber, S Butler, R Campbell, M Claborn, P Claborn, L Douglas, MT, LL Jones, Y McGinnis, B Smith, Love County Health Dept, S Makintubee, J Mallonee, MPH, G Istre, MD, Acting State Epidemiologist, Oklahoma State Dept of Health; AB Way, MD, Lubbock City Health Dept, C Reed, MPH, L Sehulster, PhD, TL Gustafson, MD, CE Alexander, MD, Acting State Epidemiologist, Texas Dept of Health; Hepatitis Br, Div of Viral Diseases, Center for Infectious Diseases, Div of Field Svcs, Epidemiology Program Office, CDC.
Editorial Note: Hepatitis A outbreaks remain a highly visible health problem in the United States, although only a small proportion of hepatitis cases are traceable to such outbreaks. In 1982, less than 7% of hepatitis cases reported to the Viral Hepatitis Surveillance Program were associated with food-borne or waterborne outbreaks (1).
Despite substantial numbers of hepatitis A infections reported each year among foodhandlers, only a few food-borne outbreaks result from such infections. In 1982, 691 infected foodhandlers were reported to CDC, but only eight food-borne or waterborne epidemics were reported (1). This suggests that contamination of food by infected foodhandlers is uncommon. Since cooking inactivates the virus, food-borne outbreaks of hepatitis A almost always involve only foods that remain uncooked between contamination and consumption. Most authorities accept handwashing as the single, most important environmental barrier preventing transfer of virus from feces to food. As demonstrated in the first outbreak, the presence of diarrhea in the index patient may increase risk of disease transmission in spite of a history of good handwashing.
Since the 1940s, immune globulin (IG) has been used successfully in the prophylaxis of hepatitis A if given within 2 weeks of exposure (2). In established food-borne outbreaks, which are usually recognized about 4 weeks (one incubation period) after exposure has occurred, IG is generally not useful in preventing illness.
Health departments are often asked to evaluate situations in which a lone foodhandler at a restaurant has contracted hepatitis A. If the diagnosis has been confirmed by a positive serum anti-HAV IgM, IG should be administered to all other foodhandlers at the restaurant. Because of the low risk of hepatitis transmission by a foodhandler, only rarely is IG prophylaxis recommended for patrons of the restaurant. CDC has recommended that such a program not be undertaken unless the following conditions exist: (1) the foodhandler has a positive anti-HAV IgM; (2) the foodhandler handles, without gloves, cold foods that will not be cooked before consumption; (3) the foodhandler has inadequate personal hygiene, especially failure to wash hands after defecation; (4) the patrons have had repeated exposures to these foods; (5) IG can be administered within 2 weeks of the last possible exposure (3).
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