Presence of pathogen in association with a host organism, where ongoing pathogen growth gives rise to disease.
Interestingly, not all infectious diseases are associated with infections as so defined…
A broader definition might replace "a host organism" with "an environment" and "disease" with "a potential to cause disease", as is the case with the phrase, "infection of with…" That broadening, however, still assumes that infecting organisms are characterized by an ability to cause disease.
It is possible therefore to define infection in some ways even more broadly, "as the acquisition of a microbe by a host." Personally, though, I would consider that definition to be describing instead the first stages of colonization, e.g., perhaps adherence. That, however, is a consequence of describing "infection" as a process that damages the body and/or causes disease.
Thus, we can consider infection as associated with or not associated with disease and also as involving or not involving microorganism growth in direct association with bodies. What's currently trending? See the definition in .