CHASING R0: UNDERSTANDING THE EFFECTS OF POPULATION DYNAMICS ON THE BASIC REPRODUCTION NUMBER

Preparation for pandemic events depends heavily on understanding specific disease characteristics and predicting the dynamics of a particular outbreak. The basic reproduction number, R-0, is an established epidemiologic statistic that provides an indication of secondary infections in the early stages of an outbreak. Assigning a specific value of R-0 to a given disease may be misleading. While an estimate of R-0 can be calculated after an outbreak has occurred, it is questionable that the same disease will manifest itself in a similar manner under different geographical and/or demographic circumstances. R-0 values for a given disease are often represented as a single number or a narrow range of numbers. The experiments discussed in this paper support evidence that a change in population-dependent parameters may affect the value of R-0, even though the disease parameters stay constant. When the contact rate, subpopulation interaction, or neighborhood size is adjusted, R-0 values fluctuate accordingly. This suggests that the value of R-0 is too complex to be attributed to a specific disease with no consideration of other factors that influence the course of disease spread.