HBV exposure, HBsAg positivity, and anti-HDV seroprevalence in rural communities along the Iran–Afghanistan border: a community-based cross-sectional study

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Hepatitis B virus (HBV) exposure and hepatitis D virus (HDV) antibody prevalence remain incompletely characterized in rural eastern Iran. We estimated anti-HBc seroprevalence, conditional HBsAg positivity, and anti-HDV seropositivity in three border villages. We conducted a community-based cross-sectional serosurvey with census-targeted recruitment in three villages of Nehbandan County, South Khorasan Province, Iran, during May–June 2024. All evaluable specimens were tested for total anti-HBc. HBsAg was measured only in anti-HBc-positive specimens, and anti-HDV was measured among participants with a final HBsAg-positive classification. Correlates of anti-HBc positivity were estimated using Firth penalized logistic regression. Of 842 residents, 494 participated (58.7%), and 489 had an evaluable anti-HBc result. Anti-HBc seroprevalence was 23.3% (114/489; 95% CI 19.6%–27.3%), including 5.3% at age ≤ 30 years and 45.3% at age > 30 years. In the primary model, age > 30 years (adjusted OR 19.36, 95% CI 10.34–38.89), Khvajeh Monji Kuh residence (4.50, 2.46–8.46), and family history of HBV (2.52, 1.12–5.62) were associated with anti-HBc positivity. The family-history confidence interval included 1 after adding education and occupation. Among anti-HBc-positive participants, 42/114 (36.8%, exact 95% CI 28.0%–46.4%) were HBsAg positive. Anti-HDV seropositivity was 5/41 (12.2%, 4.1%–26.2%). Fifteen HBsAg-positive participants initiated treatment after specialist assessment. HBV exposure was concentrated among older participants. Village comparisons were descriptive because participation differed substantially, and family-history estimates were sensitive to model specification. Birth-cohort analyses did not establish an additional cohort association beyond flexible adjustment for attained age.Staged testing prevented estimation of population HBsAg prevalence. Anti-HDV seropositivity supports antibody screening followed by HDV RNA testing to establish active infection.