Are pandemics a necessary evil? The role of epidemiological and immunological models in understanding and preventing diseases

This chapter aims to look into the modal aspects of pandemics: what is necessary and possible with regard to pandemic events (both on the individual and population levels, as well as during and between pandemic events). Tackling the title question of whether pandemics are a "necessary evil" allows us to investigate underexplored aspects of philosophy of epidemiology, which is still a somewhat neglected area of the philosophy of science. Especially the notion that pathogens naturally and necessarily evolve towards being less virulent, i.e., "milder," will be scrutinized. By developing a clearer notion of what is possible, necessary, more or less likely, almost certain, etc., we can as a society better estimate the diverse risks of zoonotic spillovers and future pandemic events. The likelihood of future pandemics seems inevitable; in that sense, the title question needs to be answered in the affirmative: yes, pandemics appear to be a necessary evil. However, that does not mean that nothing can be done about them. There are many ways in which we can make their occurrences less likely and less frequent. We can also make our population more robust, and reduce the individual risk level with preventive and protective measures, including a proper understanding of host-virus coevolution and what the immune system can and cannot do. A key component will be better concepts, models, and prediction tools, thus calling for the involvement of philosophers of science, for which the discussions of how-possibly models will be particularly informative.