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Mathematical Biosciences and Engineering (MBE)
 

The discounted reproductive number for epidemiology

Pages: 377 - 393, Volume 6, Issue 2, April 2009      doi:10.3934/mbe.2009.6.377

 
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Timothy C. Reluga - Department of Mathematics, Pennsylvania State University, State College, PA 16802, United States (email)
Jan Medlock - Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520, United States (email)
Alison Galvani - Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520, United States (email)

Abstract: The basic reproductive number, $\Ro$, and the effective reproductive number, $R$, are commonly used in mathematical epidemiology as summary statistics for the size and controllability of epidemics. However, these commonly used reproductive numbers can be misleading when applied to predict pathogen evolution because they do not incorporate the impact of the timing of events in the life-history cycle of the pathogen. To study evolution problems where the host population size is changing, measures like the ultimate proliferation rate must be used. A third measure of reproductive success, which combines properties of both the basic reproductive number and the ultimate proliferation rate, is the discounted reproductive number $\mathcal{R}_d$. The discounted reproductive number is a measure of reproductive success that is an individual's expected lifetime offspring production discounted by the background population growth rate. Here, we draw attention to the discounted reproductive number by providing an explicit definition and a systematic application framework. We describe how the discounted reproductive number overcomes the limitations of both the standard reproductive numbers and proliferation rates, and show that $\mathcal{R}_d$ is closely connected to Fisher's reproductive values for different life-history stages.

Keywords:  reproductive number, ultimate proliferation rate, game theory.
Mathematics Subject Classification:  Primary: 92D15, 92D25; Secondary: 91A22, 91A40.

Received: September 2008;      Accepted: November 2008;      Published: March 2009.