Background & objectives: Andaman and Nicobar Islands, is the home of six primitive tribes. No information is available on the prevalence of hepatitis B virus (HBV) infection among them. Hence a study was undertaken with the objective of assessing the sero-prevalence of HBV infection among the four accessible tribes of these islands.
Methods: A total of 1266 serum samples were collected from four tribes i.e., Nicobarese, Shompens, Onges and Great Andamanese and tested for the presence of HBsAg and anti-HBs. Information about different risk factors associated with HBV infection was also collected from the Nicobarese tribe.
Results: The overall seropositivity rate of HBsAg among the Nicobarese was 23.3 per cent (95% C.I. 21.0-25.9). Hepatitis B was also found to be an important health problem among the Shompens and Onges with HBsAg positivity of 37.8 and 31.0 per cent respectively. The age-wise distribution of these serological markers among Nicobarese tribe indicate that the infection is very common in all the age groups. The sero-prevalence was also found to be very high among the children.
Conclusions & interpretation: The findings of the present study indicate that hepatitis B infection is hyper endemic among the primitive tribes of these islands. Though none of the risk factors studied in the Nicobarese was found to be significantly associated with HBV infection, the fact that almost 20 per cent of the women in the reproductive age group were positive for HBsAg indicates the possibility of vertical transmission among the Nicobarese. Further studies are required to find out other modes of transmission.