This is because it doesn't pass from person to person — only from mouse to mouse, and from mouse excretions to one unlucky person or another, each of whom represents a dead-end host.
Humans are always likely to remain what biologists call a "dead-end host," one that can be infected, but whose immune system almost always prevents the virus from multiplying enough to be passed back to mosquitoes and then other hosts.
An exotic plant with foliage that is toxic to caterpillars can be a dead-end host for a native butterfly species.
Overall, most zoonotic pathogens are either not transmissible (directly or indirectly) between humans at all (i.e., humans are a dead-end host) or are only minimally transmissible.
Often, humans represent a dead-end host for these pathogens, and person-to-person transmission is rare if appropriate infection control practices are followed.
Infection from the reservoir species to another mammalian host can, and still does occur, but the non-reservoir animal most likely becomes a dead-end host.
Some pathogens may increase to a high enough load in their hosts to be infectious; others may cause nothing more than a measurable serologic response in what is otherwise a dead-end host (though explicitly known dead-end hosts have been excluded from these analyses).
DOI: http://dx.doi.org/10.7554/eLife.04395.003 Humans represent a dead-end host for the virus, with only stuttering chains of transmission reported between humans in the majority of previous outbreaks (Chowell et al., 2004; Legrand et al., 2007) and no indication that humans can reintroduce the virus back into reservoir species (Karesh et al., 2012).
The lack of current evidence for scrapie transmission to BHS could simply be due to insufficient surveillance, but other explanations, such as different susceptibilities by varying routes of exposure between domestic sheep and BHS or BHS being a "dead-end" host for scrapie, should also be explored.
A more extensive set of samples might uncover RacPyV viremia and shedding sites, but it is also worth considering that the raccoon might be a dead-end host for viral replication and that viral persistence and shedding might occur in a different species.
Our results show that testing of dead wild animals for EBOV should not be neglected and may improve our knowledge regarding the full range of dead end hosts.
