Super El Niño weather patterns may increase Sin Nombre hantavirus risk in US Southwest this summer

A developing "super El Niño" event could elevate hantavirus infection risk across the US Southwest by indirectly boosting deer mouse populations through increased rainfall and vegetation growth. Researchers cite the 1993 Four Corners outbreak—when above-average precipitation fueled a trophic cascade of vegetation → rodent food/shelter → population expansion—as a potential analog. Warmer winters may also extend rodent breeding seasons. The primary concern is Sin Nombre virus (not Andes strain), transmitted via contact with infected rodent urine, droppings, or saliva in enclosed spaces; it carries ~60% case fatality for hantavirus pulmonary syndrome. Public health authorities emphasize that infections remain sporadic and largely preventable through home sealing, proper droppings disinfection, and rodent exclusion measures.