A recent deadly hantavirus outbreak linked to a Chile-based cruise ship has thrown a long-overlooked public health threat back into the global spotlight, highlighting decades of underinvestment in developing life-saving countermeasures for the rare but lethal rodent-borne virus. Unlike the COVID-19 pandemic pathogen, hantaviruses — a diverse family of viruses documented globally for over half a century — have never drawn the sustained funding needed to advance viable treatments or licensed vaccines, even as rising human-rodent contact driven by climate change threatens to make outbreaks more common. Hantaviruses typically spread to humans when individuals inhale aerosolized particles contaminated with rodent excrement, with different regional strains triggering a range of dangerous symptoms. The Andes virus, the strain at the center of the cruise ship incident, is uniquely concerning among hantaviruses: it is the only strain confirmed to spread between humans in limited scenarios. With an overall mortality rate as high as 35% for some North American strains, the virus qualifies as a serious public health priority, according to leading researchers. The cruise ship outbreak, which resulted in three deaths out of 13 confirmed cases among passengers, fits a pattern of rising regional infection rates: Chile has recorded 15 deaths and 42 confirmed cases this year alone, while Argentina has reported 32 deaths and 102 cases since June 2025. For decades, research teams across Chile, Argentina, the United States and Germany have worked to develop effective interventions, but a lack of consistent backing from governments, global health bodies and pharmaceutical companies has stalled progress. Rarity of human infections, limited person-to-person spread, and a perceived small commercial market for treatments have all deterred the large-scale investment required for rigorous clinical safety and efficacy testing. However, new preliminary research published this week has offered a glimmer of hope, and researchers are hopeful the renewed attention from the cruise outbreak will accelerate progress. A team led by Dr. Fernando Tortosa of Argentina’s National University of Río Negro reported promising results for tocilizumab, an existing drug approved to treat rheumatoid arthritis, in treating hantavirus pulmonary syndrome — the life-threatening complication that causes fluid to build up in the lungs and triggers organ failure. Tocilizumab works by suppressing IL-6, a molecule that drives damaging inflammation in autoimmune conditions; researchers hypothesize the same inflammatory pathway is responsible for the most severe hantavirus cases. In an ongoing compassionate use trial at an Argentinian hospital, four out of five patients who received tocilizumab alongside standard supportive care survived. By contrast, all five eligible patients who did not receive the drug (due to supply shortages and rapidly declining health) died from the infection. While researchers caution the control group was older and sicker than the treatment group on average, the results are compelling enough to warrant large-scale follow-up research. Other research programs are also advancing, if slowly. A team including Chilean virologist María Inés Barría, U.S. National Institutes of Health researchers and German scientists from the Robert Koch Institute is developing a passive antibody treatment that uses cloned antibodies from hantavirus survivors to fight infection. The approach proved effective in animal trials published in 2018, but development stalled after funding was diverted to the COVID-19 response, with no progress toward human trials to date. Multiple other research groups in the U.S. are also pursuing antibody-based interventions, while several vaccine candidates are in different stages of development. While limited vaccines for some Old World hantavirus strains have been developed regionally, no hantavirus vaccine is currently licensed for widespread global use, according to the World Health Organization. One candidate targeting the Andes virus, developed by a team led by Jay Hooper of the U.S. Army Medical Research Institute of Infectious Diseases, successfully induced protective antibody responses in early-stage human trials back in 2020, but has not advanced to full approval. Experts note that significant barriers remain to bringing safe, effective interventions to market. Dr. Paul Bollyky, an infectious disease researcher at Stanford Medical Center, explained that rare, sporadic pathogens like hantavirus face unique structural challenges to research and development. Many labs lack the specialized infrastructure needed to test and validate countermeasures for rare pathogens, and the unpredictable nature of hantavirus outbreaks makes large-scale clinical trials logistically and financially impractical. The small, unsteady commercial market for a hantavirus vaccine or treatment also discourages private pharmaceutical investment, since it is impossible to predict who will be exposed and when. Despite these hurdles, researchers argue the new findings and renewed attention from the cruise ship outbreak create a critical window to advance progress. “I hope this situation will help us continue our research and strengthen the collaboration between healthcare workers, the community, and the necessary resources,” Tortosa said, noting that the current tragedy holds lessons for addressing underfunded public health threats beyond hantavirus. Barría added that her team’s antibody research is now on the cusp of moving into human trials, representing a long-awaited step forward in decades of work.
Tools to fight hantavirus show promise despite limited funding. Now researchers hope to continue
