Timeline
How the outbreak unfolded
A reconstructed sequence of events from the first reported case through today, drawn from CDC briefings, state health departments, and on-the-ground reporting.
Apr 12, 2026
First case reported
A 34-year-old hiker is admitted to a Mammoth Lakes clinic with severe respiratory distress. Initial diagnosis: atypical pneumonia.
Apr 18, 2026
Sin Nombre virus confirmed
CDC laboratory testing confirms Hantavirus Pulmonary Syndrome. The first patient does not survive.
Apr 23, 2026
Second cluster identified
Three additional cases reported across two seasonal cabins in Mono County. Investigators arrive on site.
Apr 29, 2026
State of alert declared
California issues a public-health advisory for the eastern Sierra region. Cabin owners advised on safe cleaning.
May 2, 2026
Multi-state spread confirmed
Cases identified in Nevada, Utah, and Arizona — all linked to recent travel or rural property activity.
May 5, 2026
Federal task force launched
HHS announces a four-state coordinated response with the CDC leading field epidemiology.
May 8, 2026
Case count reaches 47
Fourteen new confirmed cases since Monday. Five fatalities to date. Investigations remain active.