I am a virologist. I have spent much of my career studying high-consequence microbes such as the Ebola virus, Lassa fever virus and hantaviruses, including the Andes species confirmed in the recent outbreak. My goal has always been to understand how such viruses make us sick and to use that information to develop treatments or, ideally, to prevent infections altogether.
In this type of work, governmental support for research is critical. The potential threat of outbreaks is clear in recent headlines about the Ebola virus outbreak in the Democratic Republic of Congo and Uganda, and, closer to home, one of the American cruise ship passengers potentially exposed to the hantavirus outbreak being ordered to remain in quarantine facilities in Nebraska.
Although much remains to be learned about hantaviruses, there are some things we know.
In 2020, a group of colleagues and I studying hantaviruses were approved for five years of funding through the National Institutes of Health/National Institute of Allergy and Infectious Diseases’ Centers for Research in Emerging Infectious Diseases program. We closely collaborated with Argentine scientists on a newly emerged hantavirus closely related to the Andes virus found in rodents that had already caused disease in humans. Unfortunately, as priorities shifted at NIH, the program was not renewed last year.
Although much remains to be learned about hantaviruses, there are some things we know:
Typically, hantavirus infections are the result of direct or airborne contact with rodents or their excrement; the outbreak traced to the MV Hondius cruise ship is associated with one of the more severe species, the Andes virus. It is known to circulate in rodents found in southern South America, mainly in Argentina and Chile. It is the only hantavirus with documented person-to-person spread and has a long incubation period — up to eight weeks.
Most of my work with hantaviruses has been in the setting of a high-containment laboratory where the virus can be safely studied and tested. Hantavirus infections with a variety of strains occur all over the world and are rare — the United States averages 10 to 20 cases a year. But in Argentina, there has been a steady increase in cases, presumably from changes in rodent populations. Infections have progressed to very serious disease in some people. We do not really understand yet what mild infections look like for the Andes virus or how often they occur.
We do not really understand yet what mild infections look like for the Andes virus or how often they occur.
Often, colleagues and I also work with highly trained field biologists with expertise in rodent ecology who help us better understand how changes in rodent behavior can impact the risk to humans. Such research can offer information about how long a specific virus strain has been circulating and whether it has spilled over into humans — data crucial to navigating current and future outbreaks.
While situations like the MV Hondius outbreak are rare, they underscore why investment in the research necessary to understand these pathogens is critical. While there has been some financial support by government agencies to develop a few candidate drugs and vaccines for medically important hantaviruses, none are approved by the Food and Drug Administration, and it is not clear if there is a large enough market to incentivize Big Pharma. That leaves no options for prevention or treatment for those living in or traveling to areas where these viruses circulate.
And in our increasingly interconnected world, more and more viruses circulate. Expanded access to previously remote areas means greater risks of encountering exotic wildlife and the microbes they carry. Debates about deforestation and wildlife habitat disruption tied to agriculture plans or infrastructure development such as roads or pipelines tend to focus on typical interactions and consequences. Outbreaks remind us that we have to consider worst-case scenarios, too, when disrupting the natural world. Some local health specialists think Argentina’s increase in Andes virus cases in recent years is tied to changes in temperature, part of climate change, that are contributing to expansion of rodent populations.
Travel, too, can result in the importation of highly pathogenic viruses. This is not a new problem but one our society is woefully unprepared to deal with. A case of Lassa fever in Iowa in 2024 resulted in 180 contacts though just one fatality. During the Ebola outbreak a decade before that, there were two fatalities in the U.S., though rapid identification and contact tracing helped contain the spread. In 2018, another Andes virus case was imported to the U.S. by a vacationer. As with the recent cases, there were limited treatment options available for these patients or their close contacts.
Although some research has been done on the Andes virus, there is still much to learn about how it behaves in the context of an outbreak. Among my top questions as a virologist concerned about future outbreaks:
Are there other hantaviruses related to the Andes virus circulating that can cause disease in humans? Can humans carry the virus or shed it without symptoms? Can the virus adapt to become more transmissible among humans, as we have observed with SARS-COV-2? And, most important, can we develop and license drugs or vaccines to stop this and other viruses from causing more harm?
Addressing these questions and the inevitable follow-ups requires ongoing support of national governments. Programs such as the NIH/NIAID CREID program, the National Science Foundation’s Emerging Infectious Disease program, the NIH Fogarty International Center and others have offered critical support for collaborative research to scientists worldwide. This work has helped answer similar questions for a host of other emerging viruses and has generated data critical for addressing these high-priority pathogens when they emerge. That benefits people around the globe.
The French microbiologist Louis Pasteur said, “In the fields of observation, chance only favors the mind which is prepared.” Outbreaks like the one on the MV Hondius will continue to happen. The only way we will be ready when they occur is by continuing to invest in the scientific research necessary to ensure we understand the risks and have the means to respond.
Robert W. Cross, Ph.D., MPH, is an associate professor in the Department of Microbiology & Immunology at the University of Texas Medical Branch. His research is centered on the biology and pathogenesis of high priority viral agents.