Figure. Results of the nonlinear regression analysis between species diversity (expressed as Simpson diversity index, Ds) and Sin Nombre virus prevalence among deer mice (Peromyscus maniculatus) at each of 5 parks in Portland, Oregon, USA. The best fit model was of the form Y = x / (ax + b), R2 of 0.9994, p = 0.00001. The figure represents a summary of the results in that it shows the averages of all the seasons, in all years, in each park (indicated by circles). A regression using individual seasons and parks shows the same results.