A sero-epidemiological cross-sectional study of hepatitis B virus in Zimbabwe

Abstract

Objective: To estimate the prevalence of hepatitis B viral markers.

Design: A sero-epidemiological community-based cross-sectional study.

Setting: All nine provinces of Zimbabwe.

Participants: From April 1989 to December 1991 serum samples were collected from 1,461 males and 1,933 females in the age group 10-61 years, the majority in the younger age groups.

Main outcome measures: Sera were tested for hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), antibody to HBs-Ag (anti-HBs), antibody to hepatitis B core antigen (anti-HBc) and antibody to hepatitis B e antigen (anti-HBe). All sera were tested for HBsAg, anti-HBs and anti-HBc but for the detection of HBeAg and anti-HBe, only samples positive for HBsAg were examined.

Main results: The male-to-female ratio in rural and urban settings was 0.82 and 0.66 respectively. The median age for males and females in rural areas was 21 and 22 years and 28 and 26 years respectively in urban areas. The overall prevalence of HBsAg was 15.4% (males 16.8%, females 14.3%). The difference between sexes was consistent in all age groups and statistically significant (P < 0.05). The prevalences in urban and rural areas were almost identical (15.7% v. 15.3%). However, the prevalence was significantly higher among males in the age group 40-49 years in urban areas compared with rural areas (P < 0.0001). Using the case-referent approach, with HbsAg-positive patients as cases and HBsAg-negative ones as referents, the crude odds ratio for rural areas compared with urban areas was 0,97. However, standardisation for year of data collection and province resulted in a relative risk of 2.0, i.e. the risk of being HBsAg-positive in rural areas is twice as high as in urban areas. Similarly, the crude odds ratio for females compared with males was 0.83, and was reduced significantly to 0.7 when standardised for year of data collection and province. The prevalences of HBeAg, anti-HBe, anti-HBs and anti-HBc were 25%, 25%, 45% and 36% respectively. The prevalences of anti-HBs and anti-HBc increased continuously with age and were about 70% higher in the age group 50 years and above compared with those under 20 years. The prevalence of any of the HBV markers-HBsAg, or anti-HBc -was 66% in males and 61% in females.

Conclusions: The results indicate that hepatitis B is hyperendemic in both rural and urban areas of Zimbabwe.