A subclinical infection—sometimes called a preinfection or inapparent infection—is an infection that, being subclinical, is nearly or completely asymptomatic (no signs or symptoms). A subclinically infected person is thus a paucisymptomatic or asymptomatic carrier of a microbe, intestinal parasite, or virus that usually is a pathogen causing illness, at least in some individuals. Many pathogens spread by being silently carried in this way by some of their host population. Such infections occur both in humans and animals.