 The genus is found from Mexico to Tierra del Fuego and includes approximately 17 species.In Argentina and Chile, "Oligoryzomys longicaudatus" and other members of the genus represent the reservoir for the hantavirus strain Andes virus (ANDV) (Wells et al., 1997; Levis et al., 1998; Cantoni et al., 2001).The genus "Oligoryzomys" is included in the subfamily Sigmodontinae of the family Cricetidae.