A localized disease is an infectious or neoplastic process that originates in and is confined to one organ system or general area in the body, such as a sprained ankle, a boil on the hand, an abscess of finger. A localized disease is an infectious or neoplastic process that originates in and is confined to one organ system or general area in the body, such as a sprained ankle, a boil on the hand, an abscess of finger.