“Coevolution of Hosts and Parasites”, 1982 (; similar):
The present paper aims to take a line that is somewhat more empirical than most of the previous theoretical work. Defining parasites broadly to include viruses, bacteria, protozoans and helminths, we observe that the virulence of a parasite (the rate at which it induces host mortality) is usually coupled with the transmission rate and with the time taken to recover by those hosts for whom the infection is not lethal.
Specifically, in mice, men and other vertebrates (1972) and in many invertebrates (1975; Anderson & May 1981) low virulence is generally associated with effective immunological or non-specific responses which tend to suppress pathogen replication, with a concomitant reduction in transmissibility. Using data for the epidemiological parameters characterizing the various grades of myxoma virus infecting rabbits in Australia, we show how in this particular case virulence maybe expected to evolve to an intermediate value; the analysis appears to accord with the observed facts.
Other examples are discussed in a more qualitative way. In general, we conclude that the complicated interplay between virulence and transmissibility of parasites leaves room for many coevolutionary paths to be followed, with many endpoints.
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