Moderna — the Kendall Square outfit that turned a generation of Americans into household-name vaccinologists during COVID — signed a research deal in September 2023 with Korea University's Vaccine Innovation Center to co-develop an mRNA hantavirus shot under Moderna's mRNA Access program. In February 2025, the Korea team, led by Professor Park Man-sung, announced that experimental doses had successfully prevented hantavirus infection in mice. That is where the program currently sits. No human trials. No timeline.

Moored off the coast of Cape Verde is the MV Hondius, a Dutch-flagged polar expedition cruise ship with three dead passengers and at least eight hantavirus cases — two laboratory-confirmed and several more under investigation. The strain is the Andes virus, the only hantavirus species that spreads person-to-person. Past Andes virus outbreaks have killed up to 40% of the people they infected. The CDC pegs the case-fatality rate of hantavirus pulmonary syndrome generally at 38%.

The first two victims, a Dutch couple, are believed to have been infected before they ever boarded — picked up while bird-watching through Argentina, Chile, and Uruguay, the WHO said this week. A German national has also died.

By the time anyone outside the Hondius understood what was happening on it, the virus was already gone. On April 24 — almost two weeks after the first passenger died — more than two dozen people from at least 12 countries simply got off the ship and went home, PBS NewsHour reported. No screening. No tracing.

That cohort is now scattered across four continents, and US public-health officials are playing catch-up. Authorities in Arizona, California, Georgia, Texas, and Virginia are actively monitoring seven returning passengers for symptoms, Live Science reported Friday.