We confirmed that our model reproduced the observed slight downward trend in the rate of discovery since 1954 (figure 1) and the observed variance in the data from 1954 to 2006 (figure 2). The distribution of the number of virus species discovered per year shows slight overdispersion (meanZ2.69; varianceZ3.07; varianceto-mean ratio greater than 1) which falls within the predicted range (meanZ2.70 with 95% credible interval 2.41-3.00; varianceZ3.03 with interval 1.99-4.49). Together, these results support our choice of model, even though we do not explicitly consider heterogeneity in the probability of discovering a given species in any one year ( p) or temporal variation in sampling effort, detection techniques and reporting.