Human viruses: discovery and emergence

Woolhouse, Mark; Scott, Fiona; Hudson, Zoe; Howey, Richard; Chase-Topping, Margo

We compared the model with the observed data by calculating the mean, trend in the mean and variance for the number of virus species discovered per year (based on 5 million simulations using best fit parameter values). The model reproduces the observed data well: observed mean and variance 3.37 and 3.35, respectively; fitted mean and variance 3.36 and 3.41, respectively. Parameter estimates, however, are very uncertain owing to an unavoidable strong correlation between N and p [5] . The estimate of N is of particular interest: this has a central value of 484 (i.e. 265 species remaining to be discovered), a lower 95% CI of 308 (89 remaining), an upper 90% CI . 2000 and an upper 95% CI that is undefined. Thus, although there is considerable uncertainty as to the size of the human virus species pool, this analysis suggests that there are at least dozens of new species to be discovered, and possibly a very much larger number.