Infestation is the state of being invaded or overrun by pests or parasites.[1] It can also refer to the actual organisms living on or within a host.[2]
An internal (or endoparasitic) infestation is a condition in which organisms live within the host and includes those involving worms (though swimmer's itch stays near the surface).
Medically, the term "infestation" is often reserved only for external ectoparasitic infestations[5] while the term infection refers to internal endoparasitic conditions.[6]