By Liz Highleyman

Direct blood exposure -- for example, sharing needles for drug injection or needle-stick accidents in a healthcare setting -- is the most common route of hepatitis C virus (HCV) transmission. Several other transmission routes (including sexual activity) have been confirmed or hypothesized, but 20% of people with hepatitis C do not know how they became infected.

In developing countries, unsafe medical injections and transfusions of unscreened blood are responsible for many cases of hepatitis C, but cannot account for a substantial proportion of infections. Some investigators have suggested that intrafamilial or household transmission may play a role in countries where HCV is endemic.

As described in the September 2008 issue of Gut, French and Egyptian researchers aimed to investigate family clustering of HCV infections in a population living in a highly endemic area. They conducted a large seroepidemiological survey that included 3994 individuals from 475 familial clusters in a rural area of Egypt; participants ranged in age from 2 to 88 years.

Epidemiological methods were used to estimate risk factors and familial dependences for HCV infection. A phylogenetic analysis was conducted to investigate similarity of HCV strains within and among families.

Results

• The overall HCV seroprevalence rate was 12.3%, and the rate increased with age.

• After adjusting for relevant risk factors, highly significant intrafamilial resemblances in HCV seroprevalence were observed:

• between fathers and their children (odds ratio 3.4);

• between mothers and their children (odds ratio 3.8);

• between siblings (odds ratio 9.3).

• A weaker correlation was observed between spouses (odds ratio 2.2).

• Phylogenetic analysis showed greater similarity of HCV strains between family members than between unrelated individuals.

These findings indicate, the study authors wrote, that correlations of HCV infections among family members "can be explained in part by familial sources of virus transmission."

Furthermore, more detailed analysis of correlations between first-degree relatives suggested that genetic factors may make some individuals or family groups more susceptible to HCV infection.

"Current HCV infection in endemic countries has a strong familial component explained, at least partly, by specific modes of intrafamilial viral transmission and by genetic predisposition to infection," the researchers concluded.

Institut National de la Santé et de la Recherche Médicale, Paris, France; Université Paris Descartes, Faculté de Médecine Necker, Paris, France; Ain Shams University, Cairo, Egypt; Institut Pasteur, Paris, France; INSERM, UMR S 525, Paris, France; UPMC Paris 6, UMR S 525, Paris, France; National Liver Institute, Menophya, Egypt; National Hepatology and Tropical Medicine Research Institute, Cairo, Egypt; Institut Pasteur, Hôpital Paul Brousse, Villejuif, France; INSERM, Centre Investigation Clinique 04, Hôtel-Dieu, Nantes, France; Department of Microbiology, Minia Faculty of Medicine, Minia, Egypt .

9/19/08

Reference
S Plancoulaine, MK Mohamed, N Arafa, and others. Dissection of familial correlations in hepatitis C virus (HCV) seroprevalence suggests evidence for intrafamilial viral transmission and genetic predisposition to infection. Gut 57(9): 1268-1274. September 2008. (Abstract).