The CDC has told US clinicians to watch for hantavirus pulmonary syndrome in returning travelers after an Andes virus (ANDV) cluster broke out aboard a Southern Atlantic expedition cruise. In Health Alert CDCHAN-00528, issued May 8, 2026, the agency reported eight cases — six confirmed, two suspected — including three deaths, citing WHO figures.

The ship, identified by European authorities as the M/V Hondius, departed Ushuaia, Argentina, on April 1, 2026. Citing WHO, the CDC put the manifest at 147 people (86 passengers and 61 crew) from 23 countries; the ECDC counts 149 (88 passengers and 61 crew). The vessel called at Antarctica, South Georgia, Tristan da Cunha, St Helena and Ascension Island; the ECDC itinerary also lists Nightingale Island. WHO confirmed ANDV as the cause on May 6.

What sets this cluster apart is the pathogen. ANDV “is the only type of hantavirus that has been documented to spread from person-to-person,” the CDC notes, adding that such spread “has typically required close, prolonged contact with a symptomatic person.” Among patients with severe respiratory symptoms, the CDC says, the case fatality rate “has been estimated at approximately 38%.”

A widening, sequenced outbreak

By the ECDC’s Communicable Disease Threats Report for week 22, the count had risen to 13 cases (11 confirmed, two probable) as of May 29, with no new deaths. The two newest cases — a Dutch citizen in home quarantine after close contact with ANDV cases aboard the ship, and a former passenger evacuated to Spain who was asymptomatic — were both classified as confirmed asymptomatic cases after the ECDC revised its case definition to align with WHO (laboratory confirmation by PCR and/or serology). The ECDC’s working hypothesis is that some passengers were exposed to ANDV in Argentina before boarding and may have transmitted it to others onboard.

Andes virus is the only hantavirus documented to spread person-to-person — though the CDC says such spread is uncommon and has typically required close, prolonged contact with a symptomatic person. The ECDC’s preliminary cruise sequencing “likely” indicates human-to-human transmission, with further results pending.

On the genomics, the ECDC wrote that preliminary analysis “confirmed a high level of genetic similarity between isolates, likely indicating an initial zoonotic spillover event followed by human-to-human transmission,” with further sequencing pending. The CDC advises airborne isolation for suspected cases and including HPS in the differential for symptomatic travelers with relevant exposure in the prior 42 days. The ECDC rates the risk to the general EU/EEA population from this outbreak as very low. This is a public-health alert, not medical advice.