Pathogen–host–environment interplay and disease emergence

Engering, Anneke; Hogerwerf, Lenny; Slingenbergh, Jan

The drivers of pathogen emergence change the overall pattern of the pathogen-host-environment interactions leading to either (i) a pathogen showing up in a novel host; (ii) a mutant pathogen with novel traits causing more frequent or more severe disease while remaining in the same host; or (iii) an invasion process involving a novel geographic area. As shown in Figure 1 , disease emergence starts with an existing disease complex or pathogen-host-environment complex. While the three emergence categories are broadly speaking distinct, there are also grey areas, between existing and emerging disease events and at the interfaces of the three disease emergence categories. Taken together, these different sets of circumstances represent the full range of disease emergence. A brief introduction to the basics of this framework and the three distinct emergence categories is given in the present section.