Little evidence for genetic susceptibility to influenza A (H5N1) from family clustering data

Abstract

The apparent clustering of human cases of influenza A (H5N1) among blood relatives has been considered as evidence of genetic variation in susceptibility. We show that, by chance alone, a high proportion of clusters are expected to be limited to blood relatives when infection is a rare event.

Figures

Figure 1

Proportion of clusters limited to blood relatives versus the probability of infection (τ) under the null hypothesis (no variation in susceptibility). Point estimate of the observed data is represented by the solid black line; the shaded region represents the 95% confidence interval.

Figure 2

Relationship between data simulated under the null model and the observed pattern of family clustering for A) the proportion of cases occurring in clusters (given 261 total cases) and B) the average number of cases per cluster (given 36 clusters). Estimates of the mean are represented by solid lines; the shaded regions between the dotted lines show 95% prediction intervals for 1,000 simulations. The observed data are represented by the solid black lines.