Current Trends Racial Differences in Rates of Hepatitis B Virus Infection -- United States, 1976-1980
The prevalence of hepatitis B virus (HBV) infection in the United States and associated demographic and behavioral risk factors have been estimated from studies of the blood donor population and other selected populations (1-4). However, blood donors are not characteristic of the general U.S. population (4) and do not adequately estimate demographic risk factors associated with HBV infection. This report presents results from a seroprevalence study of HBV infection in a population that is representative of the general U.S. population (5) and describes racial differences in rates of HBV infection.
Serum collected in the Second National Health and Nutrition Examination Survey (NHANES II), conducted by CDC's National Center for Health Statistics during 1976-1980, was used to estimate the prevalence of HBV markers in the United States. NHANES II was a representative sample of the noninstitutionalized civilian U.S. population aged 6 months to 74 years. Demographic, socioeconomic, and morbidity data, as well as related medical and nutritional information, were collected by interview and physical examination (6). Serum was available from 14,488 (71.3%) of the 20,322 persons interviewed and examined. The distribution of age, sex, race, and region of the country was similar in adults tested and not tested for HBV markers. Of the 5843 children aged 6 months to 12 years, serum was available for testing for 2591 (44.3%). Serum was tested by enzyme immunoassay for hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc), and antibody to HBsAg (anti-HBs).
The prevalence of serologic markers for HBV infection (HBsAg, anti-HBs, or anti-HBc) in this population was 4.8%. Serologic markers were found in 3.2% of white participants and 13.7% of black participants. Among persons aged 65-74 years, 6.9% of whites and 39.6% of blacks were seropositive (p less than 0.001) (Figure 1). For children less than 12 years of age, rates of HBV infection for both races were low (black=1.6%, white=0.8%) (not statistically significant, p=0.147). For all age groups from 12 to 74 years, rates of seropositivity were lower for whites than for blacks (statistically significant differences for all groups). Within each race, the distribution of HBV markers was similar for males and females--for whites, 3.7% of males and 3.0% of females; for blacks, 13.9% of both males and females.
Of the 13,811 white and black participants tested for HBsAg, 40 (0.3%) were positive (Table 1). The prevalence of HBV carriers (i.e., persons who test positive for HBsAg) per 1000 was 1.9 for whites and 8.5 for blacks (not statistically significant).
The race-adjusted prevalences of all HBV markers were lower in the Midwest than in other regions (p less than 0.001): 3.2% in the Midwest, compared with 5.2% in the North east, 5.5% in the South, and 5.9% in the West. Reported by: TR Townsend, MD, Johns Hopkins Univ Hospital, Baltimore, Maryland. Div of Health Examination Statistics, National Center for Health Statistics; Hepatitis Br, Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.
Editorial Note: A difference in the prevalence of HBV infection by race in the United States has been suggested previously (7); however, this difference has not been studied using a statistically valid population-based sample. The availability of serum from NHANES II provided an opportunity to examine the distribution of HBV markers in the general U.S. population. However, because only 313 persons were classified as other than black or white in NHANES II, and ethnicity data were unknown for this group, prevalence estimates can be determined only for the black and white population. Since this survey represents 1976-1980, when the incidence of HBV infection began to increase, the results provide a baseline estimate of the prevalence of HBV infection (8). The change in prevalence over time can be assessed by determining the seroprevalence of HBV markers in NHANES III.
Because an estimated 50% of clinical HBV infections are not reported by existing passive surveillance systems (9), population-based prevalence estimates of HBV seropositivity are useful in developing prevention strategies. Moreover, for each clinically apparent case of acute icteric hepatitis, two to three persons have disease so mild either they do not seek medical attention or HBV is not considered in the diagnosis.
Hepatitis B (HB) immunization programs have focused primarily on selected groups at high risk for infection, e.g., persons at occupational risk for exposure to blood and body fluids, staff and residents in institutions for the developmentally disabled, and staff and patients in hemodialysis units (10). Data from surveillance in four sentinel counties suggest that those who are at the greatest risk of infection--intravenous-drug users, persons acquiring disease through heterosexual exposure, and homosexual men--are not served by HB vaccine programs (11). In addition, approximately 30% of hepatitis patients have no known source of infection (11).
Analysis of the NHANES II data also showed that a positive serologic test for syphilis was associated with HBV infection in both races (5) and reinforced that HBV infection is also a sexually transmitted disease (11,12). The higher prevalence of HBV infection in the black population and the increasing prevalence of infection during adolescence suggest that immunization of the traditionally targeted risk groups will not markedly affect the spread of infection in the United States. The NHANES II data suggest that, to prevent a substantial proportion of HBV infections, HB immunization programs need to include adolescents and young adults.
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