Alien species

A species not native to that area, usually introduced (purposely or accidentally) by human action.  Many alien species fail to thrive in their new environment, others become established and integrate into the existing ecosystem, a few are highly invasive and cause damage.  All alien species can carry equally exotic pathogens which may or may not, in turn, invade by infecting new hosts.  This is a frequent source of emerging infections of non-human animals and a potential source of new zoonoses.