The Centers for Disease Control and Prevention has recorded 890 laboratory-confirmed hantavirus cases in the United States since surveillance began in 1993, with the vast majority concentrated in a handful of Western states where deer mice and other rodent carriers thrive in rural and semi-rural environments.
A CDC map of cumulative cases through 2023 shows New Mexico leading with 122 cases, followed by Colorado with 119, Arizona with 82, California with 79, and Washington with 62. Ninety-four percent of all American cases have occurred west of the Mississippi River. The pattern reflects the habitat of the deer mouse, the primary carrier of Sin Nombre virus, which causes hantavirus pulmonary syndrome in North America.
The disease has drawn renewed attention in 2026 after an unusual outbreak aboard the MV Hondius cruise ship, which carried the Andes strain of hantavirus, the only type known to spread from person to person. That outbreak has sent 41 Americans into monitoring across 16 states and raised questions about how regional risk factors differ between the endemic Southwest and imported South American strains.
How to read the risk map
The CDC's state-level data reveals distinct geographic clustering. After the top five states, case counts drop sharply: Utah has 45, Idaho 25, Texas 49, and Oregon 27. Most Eastern states report single-digit cases or none at all. The American Public Health Association notes that the main risk groups are rural residents, forestry workers, farmers, military personnel in the field, and outdoor enthusiasts who encounter rodent habitats.
A January 2026 study found that drier, underdeveloped areas with less infrastructure correlate with higher hantavirus exposure risk, as these environments support larger rodent populations and more frequent human-rodent contact. Seasonal patterns also matter: infections spike in spring and summer when rodent populations increase and people spend more time in cabins, sheds, campsites, and homes that may have been vacant during winter.
The virus spreads through inhalation of aerosolized particles from infected rodent urine, droppings, or saliva. Rarely, infection occurs from rodent bites or scratches. The incubation period ranges from four to 42 days. Early symptoms, fever, fatigue, and muscle aches, resemble influenza. Four to ten days later, late symptoms appear: coughing, shortness of breath, and chest tightness. Among patients who develop severe respiratory symptoms, the case fatality rate has been estimated at approximately 38 percent.
There are no licensed antiviral treatments or vaccines. Early supportive care and immediate referral to an intensive care unit improve survival chances.
The cruise ship outbreak
On May 2, 2026, the World Health Organization was notified of a cluster of severe respiratory illness aboard the Dutch-flagged MV Hondius, which had departed Ushuaia, Argentina, on April 1 with 147 passengers and crew from 23 countries. The ship traveled across the South Atlantic, stopping at Antarctica, South Georgia Island, Tristan da Cunha, Saint Helena, and Ascension Island.
As of May 21, the outbreak has produced 11 cases, including nine confirmed and two probable, with three deaths, a case fatality ratio of roughly 38 percent. The ship docked in Rotterdam, Netherlands, on May 18, and sanitation is underway. No new cases or deaths have been reported since the previous update, according to the European Centre for Disease Prevention and Control.
The Andes virus responsible for this outbreak is endemic in parts of Argentina, Chile, and Uruguay. It is the only hantavirus known to spread from person to person, though such transmission is rare and generally requires close, prolonged contact with an infected individual or their bodily fluids. The current working hypothesis, according to WHO, is that the first case acquired the infection during birdwatching activities in Argentina before boarding, with subsequent human-to-human transmission occurring on the ship.
The cruise ship environment presents increased risk due to close living quarters, shared indoor spaces, and prolonged exposure, all of which may facilitate transmission among an elderly passenger population. The average age of passengers on board is 65 years.
US exposure and monitoring
CDC incident manager Dr. David Fitter said on May 14 that 41 Americans are under monitoring in three categories: 18 passengers recently repatriated to health facilities in Nebraska and Georgia; seven passengers who left the ship before the outbreak was identified and returned home; and 16 people who may have been exposed during flights where a symptomatic case was present. The symptomatic individual was on a flight from Saint Helena to Johannesburg.
States monitoring residents include Texas, New Jersey, Georgia, California, Virginia, Arizona, Maryland, Washington, New York, New Hampshire, North Carolina, Utah, and Oregon. The CDC has said the risk to the general American public remains "extremely low" and that there are no confirmed cases of Andes virus in the United States tied to the outbreak.
One former cruise ship passenger in the U.S. tested positive for hantavirus but has since tested negative. Another showed symptoms but tested negative. The CDC recommends testing only for people showing symptoms who were exposed.
The Andes virus differs from the Sin Nombre virus endemic to the United States in critical ways. The rodents that carry Andes virus, the long-tailed pygmy rice rat, have not been found in the United States. American hantaviruses do not spread from person to person. This biological barrier means the cruise ship outbreak poses a limited threat of establishing sustained transmission in the U.S.
Global context
Hantavirus is relatively uncommon globally but carries high mortality where it occurs. In 2025, eight countries in the Americas reported 229 cases and 59 deaths, a case fatality rate of 25.7 percent. Europe reported 1,885 infections in 2023, the lowest rate between 2019 and 2023. East Asia, particularly China and South Korea, continues to report thousands of hemorrhagic fever with renal syndrome cases annually, though incidence has declined in recent decades.
In the United States, hantavirus gained public attention in February 2026 when Betsy Arakawa, the wife of actor Gene Hackman, died from the disease. San Diego County also reported its first locally acquired case of 2026 in early May, underscoring that the endemic risk in the Southwest persists independently of international travel.
Health agencies emphasize that prevention focuses on rodent control: sealing homes and cabins, trapping rodents, and cleaning infested spaces while wearing masks and gloves to avoid inhaling particles. For travelers, the CDC has issued guidance to those who were on the Hondius or in contact with confirmed cases, advising self-monitoring for symptoms through the 42-day incubation period.