the behaviour of the pathogen in a host and its cells.
We argue that, for pathogens in a naive host population that spread more rapidly in younger individuals than in older individuals, natural selection weights more heavily a rise in reproductive rate.
Although the in vitro experiments have added substantially to our understanding of gene expression in bacterial pathogens, they can never completely model the conditions that a pathogen encounters in a host during infection.
Right after becoming infected, pathogen growth in a host is approximately exponential but it slows down as it reaches a maximum (CMax), at which it stops.
Habitats clearly show spatial structure, both for macro-organisms in the wild and pathogens within a host.
Although using these technologies to analyze pathogens within a host is still in its infancy, initial studies indicate that these technologies will be valuable tools for understanding how the pathogen reacts to the in vivo microenvironment.
In most cases, the main driver behind the emergence of a pathogen in a new host is increased contact between different host types.
This is not unexpected as a deterioration of host fitness generally occurs when a pathogen load increases in a host since pathogen multiplication leads to resource depletion in the host potentially leading to death or morbidity if the process is not prevented by host immune defenses [48].
Hence, we categorize EIDs into three main groups, with emergence of (i) a pathogen in a novel host; (ii) a pathogen with novel traits within the same host; and (iii) a disease complex moving into a novel geographic area.
First, how many pathogens can coexist in a host population described by a particular set of resources (e.g., tissue types) and immune environment?
The great global burden of fungal infections in animals is specially observed as a result of a pathogen-host shift or a recent introduction of a pathogen in a susceptible host population [ 2– 4].
