To the Editor: Several New World hantaviruses cause hantavirus pulmonary syndrome (HPS) in the Americas. All hantaviruses that cause HPS are hosted by the rodent family Muridae, subfamily Sigmodontinae (New World rats and mice). Since the Sin Nombre virus (SNV) was documented in 1993 (1), ≈25 sigmodontine hantavirus genotypes from the Americas have been described; each is associated with a different rodent species or subspecies. Hantaviruses have been documented in South America from Argentina, Chile, Paraguay, Uruguay, Bolivia, Brazil, Peru, and Venezuela (2), and in Central America from Costa Rica and Panama (3,4).