Changing Patterns of Groups at High Risk for Hepatitis B in the United States

Since 1982, CDC has been conducting intensive surveillance in collaboration with four sentinel counties (Denver County, Colorado; Jefferson County, Alabama; Pierce County, Washington; and Pinellas County, Florida) to determine trends in the epidemiology of acute viral hepatitis in the United States. Patients reported to these county health departments are considered to have acute viral hepatitis if they meet the following clinical criteria: presence of symptoms or signs of viral hepatitis; presence of serum aminotransferase levels higher than 2.5 times the upper limit of normal; and absence of other causes of liver injury. All cases are then classified as to the specific type of viral hepatitis on the basis of the following serologic criteria:

1. hepatitis A (HA)--patient is positive for IgM antibody to hepatitis

A virus (IgM anti-HAV).

2. hepatitis B (HB)--patient is positive for hepatitis B surface antigen (HBsAg) and/or for IgM antibody to hepatitis B core antigen (IgM anti-HBc).

3. non-A, non-B (NANB) hepatitis--patient is negative for IgM anti-HAV and negative for HBsAg and/or IgM anti-HBc.

Each patient with viral hepatitis is extensively interviewed for risk factors associated with acquiring the disease. In addition, to determine the actual source of infection for HB patients who have no identifiable source, attempts are made to obtain serum from household and sexual contacts of these patients.

From 1982 to 1985, both the overall incidence and the disease transmission patterns of HB were relatively constant (Figure 1, Table 1). During that time, three major risk factors accounted for almost half of disease transmission: male homosexual activity was reported by an average of 21% of patients; intravenous (IV) drug abuse, by an average of 15%; and heterosexual exposure (sexual contact with a known HB patient, with an HB virus (HBV) carrier, or with multiple partners) was reported by an average of 18%. Other recognized risk factors included health-care employment with frequent blood contact (5%), household contact with a known HB patient or carrier (2%), blood transfusions (2%), dialysis (1%), and residency in an institution for the developmentally disabled (1%). No cases of HB resulting from perinatal transmission were identified in these four counties. For an average of 36% of cases, no source of infection was identified.

Since 1985, although the overall incidence of disease remained stable, IV drug abuse, reported by 27% of patients, replaced homosexual activity as the major risk factor for HBV infection. The proportion of patients whose risk factor for HB was heterosexual exposure (as defined above) also increased to 24%; in contrast, the percentage of patients reporting male homosexual activity declined to 9%, and that of patients reporting health-care employment with frequent blood contact declined to an average of 1%. The percentage of patients reporting no identifiable source of infection also declined slightly, while the percentage reporting household contact, transfusions, dialysis, and institutionalization did not change from previous years. The increase in cases of HB associated with IV drug abuse occurred in three (Denver, Jefferson, Pierce) of the four counties; however, it was most striking in Pierce County and accounted for the county's sharp increase in disease incidence. Reported by: WJ Alexander, MD, JG Foster, SB Hill, R Holmes, JFE Shaw, L Wafer, Jefferson County Dept of Health; CH Woernle, MD, State Epidemiologist, Alabama Dept of Public Health. FN Judson, MD, S Minarik, M Shahan, Denver County Dept of Health; RE Hoffman, MD, MPH, State Epidemiologist, Colorado Dept of Health. PY Hu, MD, BR Pixley, Pinellas County Dept of Health; MH Wilder, MD, Acting State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs. AM Allen, MD, E Kramer, A Mares, KA Mottram, C Winegar, Tacoma-Pierce County Dept of Health; JM Kobayashi, MD, State Epidemiologist, Washington Dept of Social and Health Svcs. Hepatitis Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The recent changes in the percentage of HB cases attributable to specific groups at high risk for infection are striking. The 57% decrease in the number of HB cases among homosexual men is most likely a result of modification of high-risk sexual behavior to prevent human immunodeficiency virus (HIV) infec- tion (1). This hypothesis is supported by evidence that the incidence of new HIV infection is declining among certain cohorts of homosexual men (2) and that other sexually transmitted diseases among this group also appear to be on the decline in some areas (3). In contrast, the number of cases of HB due to heterosexual exposure increased modestly and parallels the recent increases in cases of primary and secondary syphilis that also occurred primarily among heterosexuals (3). Of more concern is the 80% increase in the proportion of HB patients with a history of IV drug abuse. Because the overall incidence rate of HB has remained relatively constant during this period, the absolute number of HB cases related to drug abuse appears to be increasing, indicating no modification of this high-risk behavior. Although most of the overall increase in IV drug abuse-associated HB found in this study was attributable to one county, similar increases nationwide have been seen in cases of HA, HB, and NANB hepatitis as reported to the National Viral Hepatitis Surveillance Program. These concurrent increases suggest that hepatitis associated with IV drug abuse is a widespread problem (4,5; CDC, unpublished data).

It is not surprising that in a sample of this size no perinatal cases of HB were reported. HBV infection in neonates usually results in subclinical infection.

Nationwide, the incidence of HB has increased steadily over the last decade in spite of the availability of a vaccine since 1982 (4). Vaccination programs and vaccine usage have focused primarily on three risk groups--health-care workers who are exposed to blood; staff and residents of institutions for the developmentally disabled; and staff and patients in hemodialysis units (6). These groups, however, account for only 5%-10% of acute HB cases. The risk groups that account for most cases--IV drug abusers, persons acquiring disease through heterosexual exposure, and homosexual men--are not being reached effectively by current HB vaccine programs.

The ability to immunize those groups at highest risk of HBV infection is severely limited for several reasons: the failure of both health-care providers and the target populations to recognize the specific groups at high risk of infection; difficulty in identifying persons with these high-risk behaviors; and difficulties in reaching these groups for delivery of vaccine and in timing of vaccination. In 1985, CDC surveyed a random sample of physicians in two cities to determine patterns of use and delivery of HB vaccine. Only one-third had given HB vaccine to anyone in the previous 6 months. When physicians were asked why HB vaccine was not routinely recommended, 55% said they did not see patients at high risk. When asked to specify the groups at high risk for HBV infection, 70% identified IV drug abusers, only 45% identified homosexual men, and very few (10%) identified heterosexuals with multiple partners or heterosexual contacts of carriers (12%). Thus, many potential vaccine providers have inadequate knowledge about who should receive vaccine (CDC unpublished data). Further, it is unknown whether medical-care providers who are aware of the groups at high risk of infection routinely obtain a history that would identify high-risk behaviors.

Adults in general and groups such as IV drug abusers in particular are extremely difficult to reach for delivery of vaccine. In addition, once persons begin those life-styles associated with a high risk of acquiring HB and can be identified as belonging to a high-risk group, they may become infected before vaccine can be given. Thus, the major obstacles to achieving an impact on the incidence of HBV infection in the United States are identifying and reaching persons before they become infected and vaccinating them in a timely manner. Failure to overcome these obstacles will necessitate consideration of a broader immunization strategy.

References

1. Centers for Disease Control. Self-reported behavioral change among gay and bisexual men. MMWR 1985;34:613-5.

2. Centers for Disease Control. Human immunodeficiency virus infection in the United States: a review of current knowledge. MMWR 1987;36(suppl S-6):12-4.

3. Centers for Disease Control. Increases in primary and secondary syphilis--United States. MMWR 1987;36:393-7.

4. Centers for Disease Control. Hepatitis surveillance report no. 51. Atlanta: US Department of Health and Human Services, Public Health Service, 1987:9-23.

5. Centers for Disease Control. Hepatitis A among drug abusers. MMWR 1988;37:297-300,305.

6. Immunization Practices Advisory Committee. Update on hepatitis B prevention. MMWR 1987;36:353-60,366.

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