Viral Hepatitis B, 2001

In 2001, 44 cases of acute hepatitis B virus (HBV) infection (0.9 per 100,000 population) were reported, with no deaths. Thirty-five (80%) case-patients were residents of the seven-county Twin Cities metropolitan area, with 27 (61%) cases in Hennepin County. Twenty-nine (66%) case-patients were male; 27 (61%) were young adults from 17 to 39 years of age. Twenty-three (52%) case-patients were white, 14 (32%) were black, three (7%) were Asian, and three (7%) were American Indian; race was unknown for one (2%) case. Although the majority of case patients were white, incidence rates were higher among blacks (6.9 per 100,000 population), American Indians (3.7 per 100,000 population), and Asians (1.8 per 100,000 population) than among whites (0.5 per 100,000 population). Hispanic ethnicity (which can be of any race), was reported for two case-patients (1.4 per 100,000 population).

Ten (23%) of the 44 reported cases were patients with documented asymptomatic seroconversions. In addition, six perinatal infections were identified in infants who tested positive for hepatitis B surface antigen (HBsAg) during post-vaccination screening. This is the first year that perinatal HBV infections have been counted separately from acute cases in adults. All six infants began hepatitis B immunoprophylaxis (i.e., hepatitis B immune globulin and HBV vaccine) at birth and completed the three-dose vaccine series. Five of these infants were age-appropriately vaccinated with second and third doses, and one was delayed in the receipt of the second dose.

Thirty-eight (86%) of the HBV case-patients were interviewed regarding possible modes of transmission. For 23 (61%) of those cases, the likely mode of transmission was sexual. Seven (18%) case-patients were men who reported having sex with men; seven (18%) reported heterosexual contact with a known carrier of HBsAg; six (16%) reported heterosexual contact with multiple partners within 6 months prior to onset of symptoms, and three (8%) gave recent histories of sex with an HBsAg-positive partner with undocumented sexual preference. One (3%) case-patient used needles to inject drugs. One (3%) case resulted from occupational exposure of an unvaccinated health care worker. In addition to the six perinatal cases, one (3%) case involved non-sexual contact with an HBsAg-positive person. Risk factors for acquiring HBV infection were not identified for the remaining 12 (32%) cases. The median age among these 12 case-patients and the six who were unavailable for interviews was 41 years (range, 20 to 68 years), which is consistent with possible sexual transmission.

The Minnesota School Immunization Law now requires HBV immunization for all children entering kindergarten and seventh grade who are not exempted. While the annual number of reported acute HBV infections in Minnesota is slowly decreasing, cases continue to occur among adolescents and adults who are at risk, despite national recommendations to vaccinate them. Due to the continued high rate of sexually transmitted HBV infections, health care providers should discuss the need for HBV testing and immunization with at-risk patients.

• For up to date information see>> Hepatitis B
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2001