Observed and fitted relative mortality risk with Onchocerca volvulus microfilarial skin load according to age-group.

Individuals <20 years old (open squares and solid line respectively); individuals ≥20 years old (open circles and dashed line respectively). The fitted sigmoid dose-response model is adjusted to the average age of the respective age groups. Shaded (grey) areas around the fitted lines represent 95% Bayesian credible intervals; error bars represent 95% confidence intervals around observations. Inset permits visual inspection of the mortality relative risk at parasite loads ≤40 microfilariae per skin snip.