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Hepatitis Surveillance

Hepatitis A

Issued April, 1996

Personal contact with a hepatitis A patient continued to be the predominant source of infection among persons with hepatitis A in 1993. The crude frequency that this potential source was reported, 34%, was similar to the rates in previous years. Many persons reported two or more potential sources of infection. Of those patients who were associated with day-care centers, 41% also reported personal contact with a hepatitis A patient, and 7% were part of a suspected foodborne or waterborne outbreak. Of those reporting contact with a hepatitis A patient, 6% also reported being part of a suspected foodborne or waterborne outbreak.

Since hepatitis A has an average incubation period of 30 days and is transmitted by the fecal-oral route, the characteristics reported by persons with hepatitis A as having occurred in the 6 weeks to 6 months prior to illness (Table 3) are generally not applicable to transmission of this virus.(2) Although homosexual men are considered at increased risk of acquiring hepatitis A,(3) the frequency with which homosexual activity was reported by persons with hepatitis A (3.6%) may be understated, since only 46% of the patients were asked the question in 1993. However, this percentage has increased in recent years. The frequency with which injection drug use was reported by patients with hepatitis A may be more reliable than in the past, since over 70% of patients with hepatitis A answered this question in 1993. These improvements lend greater validity to these data than in previous years.

Of patients reporting personal contact with a hepatitis A patient, 10% reported sexual, 45% reported household, and 45% reported other contact. Of those reporting other than sexual or nonsexual household contact, none had reported day-care-related exposures, but 8% reported being a part of a suspected outbreak.

To better define patterns of hepatitis A virus transmission, patients who reported more than one potential source of infection were assigned to only one group on the basis of their most probable source. These mutually exclusive groups are shown in Table 4. Contact with another person with hepatitis A was the risk factor most frequently cited. Association with a day-care center and international travel were the two risk factors next in importance.


Table 4. Epidemiologic and Clinical Characteristics of Patients Reported with Hepatitis A, by Age Group, United States, 1993
Percentage of Patients By Age (years)
Epidemiologic Characteristics for Prior 6 Weeks by Mutually Exclusive Groups* Total
N = 8,817+
N= 2,323
N =4,757
N= 1,682
Child/employee in daycare center 6.9 17.2 2.9 2.5
Contact of day-care child/employee 8.6 6.4 11.0 5.1
Personal contact with hepatitis A patient 22.0 29.0 21.8 12.8
Suspected food- or waterborne outbreak 2.2 1.2 2.1 3.9
International travel 6.3 8.2 5.2 6.5
Homosexual activity 4.9 0.2 6.9 3.9
Injection drug use 2.4 0.0 3.8 2.0
Unknown 46.7 37.8 46.3 63.3
Clinical Characteristics
Jaundice 83.0 81.7 85.7 76.9
Hospitalized for hepatitis 18.8 10.6 19.5 29.1
Death as a result of hepatitis 1.7 0.2 2.0 3.2
* In decreasing order of exclusion.   + Number includes age unknown.

Source: Viral Hepatitis Surveillance Program

The frequency with which the various risk factors were reported was influenced by the age of the patient. Contact with another person with hepatitis A was the most frequently reported risk factor for all age-groups, although the percentage of patients reporting this risk factor decreased with increasing age. For persons less than 15 years old, being a child in a day-care center was the next most frequently reported risk factor. For those aged15-39, contact with a day-care child or employee was the next most important risk factor. Reporting of injection drug use as a risk factor for hepatitis A dropped by 1993 to low levels (4%) for this age-group. For persons over 40 years of age, international travel and being a part of a suspected foodborne or waterborne outbreak were the next most frequent risk factors.

International travel was reported in 6% of hepatitis A cases in 1993. South and Central America were the locations visited most frequently (67% of travel-related cases in 1993). Destinations in Asia and the South Pacific were visited next most often (10% of cases in 1993). The duration of stay was 1-3 days in 17% of cases with international travel as a risk factor, 4-7 days in 15%, and more than 7 days in 68%. Among patients reporting short stays (1-3 days), over 90% reported visits to South/Central America.

Race and ethnicity were examined among hepatitis A patients with international travel as a risk factor. Hispanic patients accounted for 47%, non-Hispanic whites accounted for 43%, and Asian/Pacific Islanders for 8% of cases. Non-Hispanic blacks accounted for less than 2% of travel-related cases in 1993. There was an association between race and location visited: 92% of Hispanic patients with travel-related hepatitis A visited South/Central America, while 75% of non-Hispanics did so. Among Asian/Pacific Islander patients, 85% visited Asian/South Pacific destinations, while 0% to 7% of other races or ethnic groups visited these locations.

Because the total number of hepatitis A cases reported has changed over the years, the absolute numbers of cases for each risk factor show more accurately the trends over time for hepatitis A. The numbers of cases associated with personal contact with another hepatitis A patient during 1983-1993 have exhibited the greatest variation (Figure 2), with an increase of over 100% occurring from 1983 to 1989, followed by a comparable decrease from 1989 to 1993. Day-care-related cases increased more slowly during this period, but peaked in 1989 also, followed by a drop of 47%. The numbers of cases attributable to drug use increased steadily between 1983 and 1989, and declined rapidly to their present low level. Cases related to homosexual activity remained at low levels from 1983 through 1987. By 1989, however, there was a 3.6-fold increase in cases of hepatitis A among homosexual men, and outbreaks of hepatitis A in this population subgroup were reported. Cases among homosexual men have remained at higher levels through 1993. Foreign travel and foodborne outbreak-associated cases peaked in 1988 and declined overall since then.

Jaundice characterized an average of 85% of the reported hepatitis A cases in 1993. Although this frequency was similar across age-groups, jaundice and other symptoms are uncommon among young children infected with hepatitis A virus. Thus, reported cases substantially underestimate the infection burden among the youngest age-group. The rate of hospitalization of patients with hepatitis A has remained steady in 1993, and continues to increase with increasing age. The case-fatality rate for hepatitis A patients also increased with age, and showed a slight increase with time as well for those aged 15 and over in 1993.

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.