Transmission of human herpesvirus type 8 infection within families in American indigenous populations from the Brazilian Amazon

Background. The intrafamilial dynamics of endemic infection with human herpesvirus type 8 (HHV-8) in Amerindian populations is unknown.Methods.Serum samples were obtained from 517 Amerindians and tested for HHV-8 anti-latent nuclear antigen (anti-LANA) and antilytic antibodies by immunofluorescence assays. Logistic regression and mixed logistic models were used to estimate the odds of being HHV-8 seropositive among intrafamilial pairs.Results.HHV-8 seroprevalence by either assay was 75.4 (95 confidence interval [CI]: 71.5-79.1), and it was age-dependent (P _trend <. 001). Familial dependence in HHV-8 seroprevalence by either assay was found between mother-offspring (odds ratio [OR], 5.44; 95 CI: 1.62-18.28) and siblings aged ≥10 years (OR 4.42, 95 CI: 1.70-11.45) or siblings in close age range (<5 years difference) (OR 3.37, 95 CI: 1.21-9.40), or in families with large (>4) number of siblings (OR, 3.20, 95 CI: 1.33-7.67). In separate analyses by serological assay, there was strong dependence in mother-offspring (OR 8.94, 95 CI: 2.94-27.23) and sibling pairs aged ≥10 years (OR, 11.91, 95 CI: 2.23-63.64) measured by LANA but not lytic antibodies.Conclusions.This pattern of familial dependence suggests that, in this endemic population, HHV-8 transmission mainly occurs from mother to offspring and between close siblings during early childhood, probably via saliva. The mother to offspring dependence was derived chiefly from anti-LANA antibodies.