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Epidemiologic Notes and Reports Foodborne Hepatitis A -- Alaska, Florida, North Carolina, Washington

From 1983 through 1989, the incidence of hepatitis A in the United States increased 58% (from 9.2 to 14.5 cases per 100,000 population). Based on analysis of hepatitis A cases reported to CDC's national Viral Hepatitis Surveillance Program in 1988, 7.3% of hepatitis A cases were associated with foodborne or waterborne outbreaks (1). This report summarizes recent foodborne-related outbreaks of hepatitis A in Alaska, Florida, North Carolina, and Washington.Alaska

Between June 18 and July 20, 1988, 32 serologically confirmed hepatitis A cases among persons who resided in or had visited Peters Creek, Alaska (population 4000), were reported to the Alaska Department of Health and Social Services (Figure 1). Patients ranged in age from 1 to 54 years (median: 13 years). Between July 8 and August 14, 23 additional (secondary) cases occurred among household contacts of the original patients.

To examine potential sources of infection, the Alaska Department of Health and Social Services conducted a case-control study of the first 14 reported patients and 22 asymptomatic household members. All 14 patients and seven (32%) household members had consumed an ice-slush beverage purchased from a local convenience market between May 23 and June 10 (odds ratio (OR) cannot be calculated; 95% confidence interval (CI)=3.4-infinity). No other food-consumption or exposure category (including social events, restaurants, grocery stores, or international travel) was statistically associated with illness. The 18 other patients had also consumed the ice-slush beverage.

The ice-slush beverage mixture was prepared daily with tap water from a bathroom sink using utensils stored beside a toilet. All five employees of the market denied having hepatitis symptoms; four of these were tested and were negative for IgM antibody to hepatitis A virus (IgM anti-HAV). The fifth employee, who was one of the two persons who prepared the ice-slush beverage, refused to be tested. However, a household contact of this employee had had serologically confirmed hepatitis A in early June and reported that the employee had been jaundiced concurrently with her illness.Florida

In August 1988, the Alabama Department of Public Health noted an increase in cases of serologically confirmed hepatitis A in persons living in several areas of the state. Within 6 weeks before onset of illness, most affected persons had eaten raw oysters harvested from coastal waters of Bay County, Florida. The Florida Department of Health and Rehabilitative Services (FDHRS) contacted state health departments in neighboring and other states about hepatitis A cases in July or August 1988 in persons who had attended events serving seafood within 10-50 days of becoming ill. The 61 persons who were identified resided in five states: Alabama (23 persons), Florida (18), Georgia (18), Hawaii (one), and Tennessee (one). Patients ranged in age from 8 to 60 years (median: 31 years); all were white, and 49 (80%) were male. Fifty-nine (97%) had eaten raw oysters; one, raw scallops; and one, baked oysters. All the oysters and scallops were traced to the same growing area of Bay County coastal waters. The median incubation period between consumption of raw oysters and onset of illness was 29 days (range: 16-48 days).

To further study oyster consumption as a potential risk factor for hepatitis A, the FDHRS conducted a case-control study using uninfected eating companions of the patients as controls. Fifty-three patients who had serologically confirmed hepatitis A and 64 controls were interviewed by telephone; 51 (96%) of the patients and 33 (52%) of the controls had eaten raw oysters (OR=24; 95% CI=5.4-252.6). Consumption of other seafoods (i.e., clams, mussels, and shrimp) was not statistically associated with illness.

The implicated oysters apparently had been illegally harvested from outside approved coastal waters of Bay County. Sources of human fecal contamination were identified near oyster beds unapproved for harvesting and included boats with inappropriate sewage disposal systems and a local sewage treatment plant with discharges containing high levels of fecal coliforms.North Carolina

Beginning September 30, 1988, hepatitis A cases among employees of businesses located in east Greensboro were reported to county health departments in central North Carolina. Only day-shift employees became ill. Preliminary investigation suggested a common exposure to one nearby restaurant (restaurant A), which served as many as 400 meals per day to regular clientele. A total of 32 outbreak-associated cases was eventually reported.

The North Carolina Department of Human Resources conducted a case-control study to assess a possible association between illness and exposure to restaurant A. Twenty-seven patients and 50 controls (randomly selected from co-workers) were interviewed about exposures to different restaurants since August 15. Patients were more likely than controls to have eaten at restaurant A (OR=4.1; 95% CI=1.3-14.4). No other restaurant was statistically associated with illness.

Based on additional information obtained from 16 patients and 20 controls who reported eating lunch at restaurant A 2-6 weeks before the outbreak, only consumption of iced tea (OR=8.1; 95% CI=0.8-387.8) or hamburgers (OR=11.4; 95% CI=1.1-551.3) was associated with illness. However, 15 (94%) of the ill persons drank iced tea, whereas only six (38%) of the ill persons reported eating hamburgers.

All foodhandlers at the restaurant were tested for IgM anti-HAV; one employee, who was IgM anti-HAV-positive, denied symptoms of and risk factors for hepatitis A. However, this employee was a suspected intravenous (IV)-drug user and had job tasks that included preparation of fountain drinks and sandwiches.

Immune globulin (IG) was given to all foodhandlers at the restaurant. Because primary/secondary-case status and infectiousness of the IgM anti-HAV-positive foodhandler were unknown and because her hygiene and foodhandling practices were questionable, the local health department recommended administration of IG to all patrons who had eaten at the restaurant within 2 weeks before the association between hepatitis A and the restaurant had been determined. More than 1000 IG doses were given. The restaurant voluntarily closed for 24 days, and no persons with hepatitis A were identified with onset after November 8.Washington

In May 1989, the Seattle-King County Department of Public Health (SKCDPH) received reports of and investigated 213 cases of hepatitis A--a threefold increase over the average of 68 cases reported in each of the first 4 months of 1989. Onsets of illness clustered during April 28-May 5. One hundred seventeen (55%) of the patients had eaten at one outlet of a Seattle-area restaurant chain (chain A). One of the patients was a recent employee and three were current employees of three of the chain's restaurants. Interviews with past and present chain A employees did not identify any worker with illness during the period of likely exposure for most patients (2-6 weeks before onset of illness). All other current workers in the three restaurants were tested for IgM anti-HAV. None were positive, and all were given IG. Because two of the ill employees had poor hygiene and had worked while ill with diarrhea, the SKCDPH recommended IG for patrons who had eaten at two of the restaurants from May 3 through May 6.

The SKCDPH conducted a case-control study to further examine the potential role of chain A restaurants in the outbreak. Sixteen patients were randomly selected and re-interviewed by telephone; 16 age-group- and sex-matched controls were obtained by increasing each patient's telephone number by one. Exposure to 11 multi-outlet restaurant chains (including chain A) was ascertained for patients during the 2-6 weeks before onset and for controls during April 14-May 12. Mean total of any restaurant visits was higher among patients (7.7) than among controls (4.3). In addition, patients (89%) were more likely than controls (25%) to have eaten at restaurants from chain A (OR=11.0; 95% CI=2.2-56.0); differences in exposure to the 10 other multi-outlet restaurants were not statistically significant.

Follow-up investigation did not detect deficiencies in sanitation practices or history of recent hepatitis among employees of chain A's distributors of foodstuffs, paper goods, and related supplies. The cause of the outbreak remains undetermined. Reported by: ME Jones, MD, SA Jenkerson, MSN, JP Middaugh, MD, State Epidemiologist, Alaska Dept of Health and Social Svcs. J Benton, MD, P Sylvester, MD, Bay County Health and Rehabilitative Public Health Unit, Panama City; KC Klontz, MD, MH Wilder, MD, RA Calder, MD, State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs. CH Woernle, MD, State Epidemiologist, Alabama Dept of Public Health. RK Sikes, DVM, State Epidemiologist, Georgia Dept of Human Resources. E Veuthy, SW Wyrick, MPH, BD Weant, E Tysinger, C Rocco, MS, J Holliday, MD, Guilford County Health Dept, Greensboro; CJ Staes, MPH, RA Meriwether, MD, JN MacCormack, MD, State Epidemiologist, North Carolina Dept of Human Resources. JF Hogan, MPH, S Cummings, N Harris, DVM, CM Nolan, MD, Seattle-King County Dept of Public Health; JM Kobayashi, MD, State Epidemiologist, Washington Dept of Health. J Black, Food and Dairy Div, Oregon Dept of Agriculture; D Fleming, MD, LR Foster, MD, State Epidemiologist, State Health Div, Oregon Dept of Human Resources. Div of Field Svcs, Epidemiology Program Office; Hepatitis Br, Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The outbreaks reported here illustrate two principal modes of transmission associated with foodborne hepatitis A outbreaks: 1) contamination of food during preparation by a foodhandler infected with hepatitis A virus and 2) contamination of food, such as shellfish, before it reaches the food service establishment.

Contamination of food during preparation by a hepatitis A-infected foodhandler is the most common mode of transmission in foodborne outbreaks. The Alaska and North Carolina outbreaks are atypical in that ice or drinks as vehicles are rare; usually the vehicles are sandwiches or green salads that are not cooked or are improperly handled after cooking. The outbreak in North Carolina is also consistent with a nationwide phenomenon of increased reports of hepatitis A among IV-drug users (2), who can become sources of foodborne outbreaks if they are also foodhandlers.

Contamination of food with virus before the food reaches the service establishment is less common. Shellfish filter large quantities of water during feeding and in the process can concentrate microorganisms, including enterically transmitted viruses such as hepatitis A (3). Transmission to humans occurs when contaminated shellfish are consumed raw or undercooked. Hepatitis A outbreaks attributed to consumption of contaminated shellfish have been reported intermittently in the United States and abroad (4-8); in 1988, an outbreak associated with clams involved more than 250,000 cases in Shanghai, People's Republic of China (7). The Florida outbreak reported here is the largest attributed to shellfish in the United States since 1973 (4) and the largest ever reported in Florida. Outbreaks due to pre-retail contamination of products other than shellfish have rarely been reported. In 1988, a multifocal outbreak linked to lettuce possibly contaminated before local distribution occurred in Louisville, Kentucky (9).

Measures to prevent foodborne hepatitis A outbreaks include training of food handlers regarding proper hygiene and foodhandling practices, investigation of food handlers who have symptoms of hepatitis or are otherwise ill, prompt reporting by health-care providers to local health departments of patients with suspected foodborne hepatitis A, and prompt investigation by health departments of possible sources of infection. Consistent maintenance of good handwashing and other personal hygiene measures by foodhandlers is important because the source patient in foodborne outbreaks is often asymptomatic (as apparently occurred in North Carolina and Alaska). Prevention of hepatitis A outbreaks associated with shellfish relies on surveillance of water beds where shellfish are harvested to ensure that there is no evidence of fecal contamination. Transmission and infection from shellfish also can be prevented by thorough cooking and proper storage and handling before and after cooking.

When a foodhandler is diagnosed with hepatitis A, IG is usually recommended for other foodhandlers at the same establishment (10). IG is generally not recommended for patrons because common-source transmission is infrequent; however, it may be considered if the infected person handles high-risk foods, has poor hygiene, or has diarrhea during the early stages of illness and if patrons can be identified and treated within 2 weeks after exposure (10). Once a foodborne hepatitis outbreak has occurred, it is usually too late to prevent further cases because the 2-week period after exposure during which IG is effective has already passed. The increasing number of hepatitis A cases nationwide underscores the importance of focusing on food handlers with hepatitis A and decisions regarding IG administration to food service patrons.


  1. CDC. Hepatitis surveillance report no. 52. Atlanta: US

Department of Health and Human Services, Public Health Service, 1989:19-21.

2. CDC. Hepatitis A among drug abusers. MMWR 1988;37:297-300,305.

3. Gerba CP, Goyal SM. Detection and occurrence of enteric viruses in shellfish: a review. J Food Protection 1978;41:743-54.

4. Portnoy BL, Mackowiak PA, Caraway CT, Walker JA, McKinley TW, Klein CA. Oyster-associated hepatitis: failure of shellfish certification programs to prevent outbreaks. JAMA 1975;233:1065-8.

5. Dienstag JL, Lucas CR, Gust ID, Wong DC, Purcell RH. Mussel-associated viral hepatitis, type A: serological confirmation. Lancet 1976;1:561-4.

6. Ohara H, Naruto H, Watanabe W, Ebisawa I. An outbreak of hepatitis A caused by consumption of raw oysters. J Hyg 1983;91:163-5.

7. Xie H, Cai Y, Davis LE. Guillain-Barre syndrome and hepatitis A: lack of association during a major epidemic. Ann Neurol 1988;24:697-8.

8. Mele A, Rastelli MG, Gill ON, et al. Recurrent epidemic hepatitis A associated with consumption of raw shellfish, probably controlled through public health measures. Am J Epidemiol 1989;130:540-6.

9. Rosenblum LS, Mirkin I, Allen D, Safford S, Hadler S. Multifocal outbreak of hepatitis A, Louisville, Kentucky (Abstract). In: Program of the Epidemic Intelligence Service 38th Annual Conference. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, 1989:72. 10. Carl M, Francis DP, Maynard JE. Food-borne hepatitis A: recommendations for control. J Infect Dis 1983;148:1133-5.

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