Growth rates in epidemic models: Application to a model for HIV/AIDS progression

The most common quantity used to describe the growth of an epidemic when modelling infectious diseases is the basic reproduction number R 0 . While R 0 is most appropriate for epidemics with short‐lasting infections, long‐lasting infections such as HIV/AIDS may call for the use of growth rates with other properties. For a group of multi‐state compartment models we define both R 0 , the actual reproduction number R a ( t ), and the intrinsic growth rate r . We study the relationship between these different reproduction numbers and growth rates and take a brief look at how they could be estimated from actual observed data. The work is illustrated by a model for HIV/AIDS progression among homosexual men in England and Wales. We conclude that other measures of growth, in addition to R 0 , give important supplementary information. Copyright © 2008 John Wiley & Sons, Ltd.