In April, the MV Hondius set sail from Ushuaia, Argentina, aiming to transport 147 passengers and crew to some of the world’s most isolated locations, including Antarctica. However, the journey was abruptly halted due to a rare virus outbreak, which resulted in three fatalities and infected several more individuals.
Hantaviruses, a longstanding family of pathogens transmitted by rodents, are believed to have caused human diseases long before their first documentation in the 1950s. These viruses are typically spread to humans through inhalation of dust contaminated with rodent excreta. The Andes hantavirus, which affected the MV Hondius, is among the few strains known to cause hantavirus pulmonary syndrome, a rare but often deadly condition.
Notably, the Andes strain is the only hantavirus known to be transmissible from person to person, transforming a rare rodent-borne disease into a global emergency, reminiscent of the COVID-19 pandemic response.
Fortunately, while the Andes hantavirus is particularly lethal, it is believed to be far less transmissible than COVID-19. Nonetheless, the outbreak underscores the complexities of managing infectious disease crises amid increasingly fragmented international cooperation on public health. This situation is exacerbated by a growing likelihood of global pandemics. Just a month before passengers on the MV Hondius began showing symptoms, Argentina formally withdrew from the World Health Organization, aligning with the U.S. in exiting a global health alliance designed to coordinate responses to cross-border disease threats.
This crisis highlights another pressing challenge for global health: climate change is altering environmental factors such as rainfall and vegetation, which in turn affect rodent populations. Experts caution that these changes increase the likelihood of pathogens spreading from animals to humans.
Given the hantavirus’s incubation period of one to six weeks, the outbreak could have originated from any passenger’s home country. However, one potential source might be the ship’s stop near Ushuaia for a bird-watching trip, close to a landfill that attracts rodents. Argentina’s health officials have already reported a significant increase in hantavirus cases this season, with 101 infections since June 2025, doubling the count from the previous year.
The cause of this surge remains undetermined by Argentina’s health ministry, though studies indicate climate change may be a factor. Argentina and its neighbors faced severe droughts from 2021 to 2024, including the country’s most severe dry period in over 60 years in 2023, followed by intense rainfall the next year. Kirk Douglas, a senior scientist at the University of the West Indies, Cave Hill, in Barbados, who researches hantaviruses and climate change, notes that such extreme weather, exacerbated by global warming, influences rodent behavior.
Extended droughts push rodents into urban areas in search of food, increasing human exposure to the virus. Conversely, sudden rainfall after droughts leads to an abundance of nuts and seeds, benefiting rodents and potentially increasing animal-to-human transmission.
Nonetheless, there isn’t a straightforward correlation between global temperature rise and the risk posed by rodents. Climate change isn’t the sole factor; a complex array of natural and human-induced landscape changes also affects human-rodent interactions. While increased temperatures and humidity do not seem to impact hantavirus ecology as significantly as drought and precipitation, they play a part.
“Hantavirus is sensitive to the changes climate change will bring,” Douglas stated. “It’s all dependent on what the prevailing climate impact is.”
This complexity makes the risk of hantavirus hard to predict and often overlooked. In the United States, hantavirus has been relatively rare since federal monitoring began in 1993, with fewer than 1,000 confirmed cases reported by 2023. Of these, about 35 percent, primarily located west of the Mississippi River, were fatal.
Similarly, in the U.S., the dynamics of hantavirus might be evolving. Federal researchers noted in a recent study that dry regions, characterized by scattered homes, diverse rodent populations, and limited community resources, especially in the American West, are most at risk.
