Stopping an Outbreak: Hantavirus on the MV Hondius

Although an estimated two-thirds of international travelers will develop a travel-related illness, most fevers and respiratory symptoms have self-limiting causes. A notable exception was an outbreak of severe acute respiratory illness that afflicted 13 passengers and crew members (including the ship’s doctor) on the expedition cruise ship MVHondius and caused three deaths. The first passenger to die most likely acquired the infection from a rodent in Argentina, where the MVHondius departed on April 1, 2026. Reverse transcriptase polymerase chain reaction (RT-PCR) testing confirmed that the contagious illness was hantavirus cardiopulmonary syndrome caused by the Andes virus, which had previously shown person-to-person transmissibility in crowded social settings.

A 2002 American Family Physician article called hantavirus infection “a zebra worth knowing” because, although it is rare (fewer than 900 cases have been reported in the United States since 2023), prompt diagnosis in persons with early symptoms can be lifesaving. Outside of the Andes virus, hantavirus is acquired by exposure to saliva, urine, or feces of infected rodents, such as the deer mouse in the United States.

After an incubation period of up to several weeks, patients in the prodromal phase of the illness develop fever and myalgias, lasting 3 to 5 days. Characteristic laboratory findings include thrombocytopenia, left-shifted leukocytosis, circulating immunoblasts, and hemoconcentration. The cardiopulmonary phase is heralded by the acute onset of hypotension, pulmonary edema, tachypnea, and progressive hypoxia, usually requiring mechanical ventilation within 24 hours. No specific treatment is available. Despite supportive care, the case fatality rate of hantavirus cardiopulmonary syndrome approaches 40%.

On May 18, 2026, the Centers for Disease Control and Prevention issued a health alert for US clinicians and health departments about when to consider testing patients for hantavirus infection. It is thought that transmission of Andes virus occurs only in the symptomatic phases; therefore, at least 65 US passengers and others with possible Andes virus exposures are being monitored at home by state health departments or in the 20-bed National Quarantine Unit at the University of Nebraska Medical Center.

Despite a superficial resemblance to the early days of the COVID-19 pandemic—a fatal respiratory illness spread rapidly on a cruise ship while political leaders and public health authorities assert that the risk to the general public is low—Andes virus will not become the next pandemic. (After being cleaned and disinfected, the MVHondius is scheduled to resume passenger operations on June 13, 2026.) However, the outbreak response highlighted gaps in global public health preparedness that have widened since the United States withdrew from the World Health Organization (WHO) in early 2026. A fatal outbreak on an oceangoing vessel is an international problem by definition, but efforts by various countries to contain it have been halting and inconsistent. In a JAMA commentary, Dr. Attila Hertelendy and colleagues asserted:

The principal vulnerability exposed by the Hondius outbreak lies not in sustained [viral] transmission, but in delayed recognition, fragmented authority, and inconsistent public health implementation across jurisdictions. … WHO can coordinate information sharing, issue technical guidance, and recommend public health measures, but it cannot compel states to permit disembarkation, harmonize quarantine protocols, or share responsibility for exposed travelers.