Pathogen–host–environment interplay and disease emergence

Engering, Anneke; Hogerwerf, Lenny; Slingenbergh, Jan

As shown in Figure 1 , the divide between an existing and emerging disease complex is not always clear. Flare-ups of existing diseases may interfere with, overlap with or assist new disease emergence given the fluctuations in disease prevalence and incidence. Figure 1 also elaborates on the grey areas between the three emergence categories. The disease emergence narratives presented here are mostly of recent origin, stretching over just a few decades, and matching the turbulence created by a global set of contemporary drivers bringing the rapid changes in the availability, use and management of the earth's terres-trial resources. Naturally, in such a time frame, disease emergence and pathogen evolution are based on variations of already existing forms of microbial life. A different temporal resolution would have changed the picture. All currently existing pathogens at some stage in their evolutionary history have switched host species, spread geographically and underwent character changes. Hence, when fitting EID events in the current framework, the geospatial and temporal scales of the event should be made explicit and accounted for. Using the framework here presented, most EID pathogens and disease emergence dynamics are captured with relative ease. In some cases, precise information on changes in pathogen genetics, host specificity, transmission modes, incidence and pattern or invasion dynamics relative to the pre-emergence situation is missing. Here, the framework may assist in gap analysis to reveal critical information that is missing and/or research yet to be performed.