Sin Nombre virus occurs primarily in which region?

• A. Southeastern Asia
• B. Australia
• C. Western United States
• D. Central Europe

Answer: (C)

Sin Nombre virus is a hantavirus carried primarily by deer mice in North America, and it was identified in the western United States. Human cases cluster in western states where this rodent reservoir is common, making that region the typical geographic focus. Other regions—Southeast Asia, Central Europe, and Australia—have different hantaviruses circulating in locally common rodent hosts, not Sin Nombre. So the western United States best fits the known distribution of this virus.