Multilevel modeling of intra-household spread of hepatitis C virus infection, Karachi, Pakistan.

Several epidemiologic studies have reported the existence of nonsexual intrafamilial hepatitis C virus (HCV) transmission. However, actual routes and their relative efficiency have been controversial. The objective of this study was to investigate whether contacts of HCV seropositive index patient living in the same household have similar probabilities of being HCV seropositive with respect to any of the household-level variables, after taking into account the independent effects of individual-level variables. We analyzed cross-sectional serological data on 341 nonsexual household contacts of 86 HCV-seropositive index thalassemic patients with a multilevel logistic regression model using household contacts at the first level and household characteristics at the second level. Prevalence of HCV seropositivity among household contacts who were tested was 20.5% (70/341). Multilevel analysis of household-level fixed effects indicated that contacts living in families wherein the index thalassemic patient was RNA positive--compared with those contacts living in families wherein the index thalassemic patient was RNA negative--had higher odds of being HCV positive (OR=2.09; 95% CI: 1.02 to 4.28). Nonetheless, the effect of index patients' RNA status on the contacts' HCV serostatus was small in comparison with the unexplained between-cluster variation. The results of this study are pertinent for household members of HCV-infected patients; specifically, their close contact with objects that are contaminated with blood or perhaps saliva of the HCV-seropositive index patient may pose increased risk of HCV transmission. High household intercept variances in different analyses revealed that at there are still unrecognized nonsexual modes of HCV transmission at the household level that need further research.