Proportion of Beijing (A), EAI4-VNM (C) isolates and others (B) as functions of age and location (urban in red vs. rural in blue).

Empty circles represent raw data (1 and 0 for yes and no), filled dots are the means defined for each age class (represented by vertical dotted bars and labeled on the top of the graph), together with 95% confidence interval (vertical bars). The lines are the logistic model predictions (see table 5 for the parameter estimates and their significativities) together with 95% CI (shaded area).