Western U.S.

Specific high-signal states

The Four Corners region and adjacent states carry the bulk of the historical record.

• New Mexico — among the highest cumulative HPS counts.
• Colorado — sustained signal across the Four Corners.
• Arizona — site of the original 1993 outbreak recognition.
• California — sustained historical contribution across the rural state.
• Washington, Oregon, Nevada, Utah — recurring rural exposure records.

Land use and exposure context

Hantavirus cases in the West are repeatedly linked to specific types of structures and activities: opening up cabins that have been closed for the season, cleaning out sheds and barns, working around stored hay or grain, and sleeping in poorly ventilated rural buildings where rodent populations have established.

Seasonal patterns

Many cases cluster in spring and summer, when seasonal cabins, sheds, and recreational structures are re-opened. The exposure is not strictly seasonal — it tracks the activities, not the calendar — but the activity profile rises in warmer months.

Outside the West

HPS cases occur outside the West too. The Southeast picks up cases tied to cotton rat and rice rat reservoirs; the white-footed mouse extends across the eastern and central states. Lower cumulative counts in those regions do not mean exposure is absent — they mean documented cases are fewer.

Map limits

State-level data smooths over the local detail that actually matters. A statewide 'baseline' label cannot tell you whether the specific cabin you are about to clean has had rodent activity; only inspection of the structure can.