Many traits that spread are the result of some kind symbiosis. Pathogens spread through populations - but so do mutualists - such as the relationship between humans and various kinds of fruit and vegetable. Humans also have mutualistic relationships with a variety of decorative and medicinal plants.
Other traits that spread through populations are cultural traits. These can usefully be seen as being cultural symbionts. Fads, fashions, and trends spread through populations much like plagues and viruses do. They too spread like epidemics and plagues - and have their own epidemic threshold.
Other types of phenomena spread as well - for example radioactive fallout, sunburn and frostbite.
However, not all of the phenomena that spread are particularly health related. Currently the fields of mutualisms and memetics borrow heavily from the terminology of epidemiology to describe the dynamics of the systems they study. It seems desirable to generalise epidemiology to cover all traits.
So, here we propose generalised epidemiology - the science that studies how traits spread through populations - irrespective of whether the traits are related to health. This field differs from demography through its focus on change - and through not being confined to humans.
A similar coinage is infodemiology. One paper claims:
Infodemiology can be defined as the science of distribution and determinants of information in an electronic medium, specifically the Internet, or in a population, with the ultimate aim to inform public health and public policy.That's a pretty duff definition, but the word could work. Generalised epidemiology is intended to cover infodemiology and epidemiology. However, "infodemiology" may be more of a rival term - and it is a bit of a shame that the first stab at it didn't cover the general case.
It is proposed that use of the term "epidemiology" to refer only to health traits should eventually be deprecated, allowing the term "epidemiology" be reassigned to refer to the concept of generalised epidemiology described here. This proposal is supported by the etymology of the word "epidemiology" - which says that it means, roughly speaking: "what is on the people".
This posts builds on this previous post on much the same topic.