Colorado is no stranger to hantavirus. Since federal surveillance began in 1993, the virus has killed 47 state residents, according to Hope Shuler, a spokesperson for the Colorado Department of Public Health and Environment. Only New Mexico has recorded more confirmed cases nationally. In 2024, five Coloradans contracted the virus and two died, CDPHE spokesperson Kristina Iodice confirmed.
On May 2, 2026, the World Health Organization received notification of a cluster of severe respiratory illness aboard the MV Hondius, a Dutch expedition vessel that had left Argentina on April 1. By May 13, eight confirmed cases, one inconclusive, and two suspected cases had been identified among the ship’s 149 passengers, with three dead. The culprit was the Andes strain of hantavirus — a South American variant that can spread from person to person through close, sustained contact, a capability no other known hantavirus strain carries.
CDC dispatched a team to meet the ship in the Canary Islands. American passengers were repatriated on a government medical flight to Offutt Air Force Base in Nebraska, then transferred to the Nebraska Biocontainment Unit and Emory University Hospital in Atlanta. CDC classified the outbreak as a Level 3 emergency response. The WHO coordinated multi-country contact tracing across 23 nations. Kansas confirmed three residents under observation after exposure to a returning cruise passenger — none symptomatic, no confirmed Kansas cases.
Colorado’s strain is different. The Sin Nombre virus — the strain that emerged in the Four Corners region in 1993 — spreads through deer mouse droppings, urine, and saliva and has never transmitted between humans. Of the 121 confirmed Colorado cases over 30 years, the virus killed in roughly 35 percent, consistent with the national fatality rate documented by the CDC. Hantavirus has killed more than 300 Americans since 1993. No emergency declaration, quarantine order, or federal response framework was triggered by any of those deaths.
CDC’s own incident manager, David Fitter, said at a press briefing this week that the risk to the general public from the cruise ship outbreak is low. The agency is encouraging — not ordering — American cruise passengers to isolate at home. No formal quarantine order is in place. The WHO has not declared a specific emergency level and has stated that previous Andes virus outbreaks involved transmission only in close-contact settings. CDPHE assesses the risk of the Andes strain reaching Colorado’s general population as extremely low.
Peak exposure season for Sin Nombre hantavirus in Colorado runs spring through early summer, when closed spaces disturbed by mice over winter get cleaned out. An N95 mask, open windows, and a disinfectant solution applied to surfaces before cleaning are the recommended defenses. Early symptoms mimic the flu — fever, fatigue, muscle aches — and can progress to fluid in the lungs within days. A blood test confirms infection. There is no cure and no approved vaccine. Early supportive care, including ECMO in severe cases, improves survival odds when started before the critical phase sets in.
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