The virus sticks before it reaches the cell, so infection never begins.
Carrageenan, derived from red algae, works by electrostatically binding to viral particles and preventing them from infecting respiratory epithelial cells. The drug achieved an 80% reduction in COVID-19 transmission in a multicenter hospital study and now shows similar promise against the Andes hantavirus strain.
- Carrageenan reduced COVID-19 transmission by 80% in a multicenter hospital study
- Hantavirus pulmonary syndrome has a 40% fatality rate
- Laboratory tests showed carrageenan reduced viral load in infected respiratory cells without toxicity
- The Andes strain of hantavirus can spread between humans and circulates in Patagonia
Argentine researchers confirm that carrageenan, a natural compound previously effective against COVID-19, reduces hantavirus viral load in laboratory tests without toxicity, offering potential treatment for the deadly respiratory syndrome.
A group of Argentine researchers has identified a potential weapon against one of the deadliest viruses known to medicine, and the timing could hardly be more urgent. As a cruise ship carrying hantavirus-infected passengers approaches Spanish shores for a controlled landing, scientists at the Malbrán National Reference Laboratory announced that carrageenan—a compound derived from red algae that proved effective against COVID-19—appears to block the Andes strain of hantavirus from infecting human cells. The discovery emerged from laboratory work conducted at the Molecular Biology Service of the National Institute of Epidemiology and Infectious Diseases, and the findings will be presented within days at the Argentine Congress of Virology.
Carrageenan works through a mechanism of elegant simplicity. The compound is a large, negatively charged polymer that attracts viral particles, which typically carry positive charges. When the virus encounters carrageenan molecules, it adheres to them electrostatically before it can reach a respiratory cell. The carrageenan then envelops the virus, masking the spike proteins that would normally lock onto cellular receptors. Trapped in this viscous net, the virus is carried away by mucus and either swallowed or expelled from the body, preventing viral replication in the nasal passages and lungs. In the laboratory tests, researchers demonstrated that carrageenan reduced viral load in already-infected respiratory epithelial cells without causing toxicity—a crucial finding for any potential therapeutic.
The drug's track record against respiratory viruses is substantial. During the COVID-19 pandemic, carrageenan underwent rigorous testing in a multicenter study involving hospital workers across numerous health facilities throughout Argentina. Those results, published in peer-reviewed literature, showed an 80 percent reduction in transmission rates. The compound had previously demonstrated effectiveness against common colds and influenza. Now, with hantavirus pulmonary syndrome carrying a 40 percent fatality rate, the possibility of a proven-safe antiviral agent takes on particular weight.
The research team presented preliminary findings on this work at the end of the previous year during the Argentine Congress of Respiratory Medicine. The current study focused specifically on the Epuyén strain of Andes hantavirus, the variant circulating in Argentina and capable of spreading between humans—a characteristic that distinguishes it from other hantavirus strains and makes it a public health concern. The work received recognition in September 2024 when it was awarded a Florencio Fiorini Subsidy for Research in Biomedical Sciences, supporting a project examining the role of carrageenan and surfactant proteins in viral replication and immune response across both hantavirus and SARS-CoV-2 infections.
One of the researchers involved in this current work apparently made an earlier discovery that proved controversial within the international scientific community: the demonstration that Andes hantavirus could transmit from person to person, a finding that initially met skepticism and resistance. That same scientist is now part of the team pursuing carrageenan as a treatment option.
The immediate question is whether this research could be applied to the current outbreak. The MV Hondius cruise ship, carrying infected passengers, might seem an ideal setting for an expedited clinical trial—a contained population with documented cases and a proven-safe intervention. However, the imminent disembarkation and the bureaucratic protocols governing emergency medical interventions make such a scenario unlikely, at least in the near term. The researchers instead are seeking additional funding to conduct proper clinical trials in Patagonia's high-incidence hantavirus zones, where the virus circulates among rodent populations and occasionally spills over into human communities.
Historically, carrageenan and hantavirus have barely intersected in the scientific literature. A single prior study from 2016 examined carrageenan against an Old World hantavirus strain in vitro using monkey kidney cells—not respiratory epithelial cells, and not a strain that infects humans or spreads between them. The current work represents a genuine departure, grounded in the urgent reality of a virus that kills four of every ten people it infects.
Citas Notables
The virus becomes trapped in a viscous net of carrageenan molecules and is carried away by mucus, preventing viral replication in the nasal passages and lungs.— Argentine researchers at the Malbrán laboratory
La Conversación del Hearth Otra perspectiva de la historia
Why does carrageenan work differently against hantavirus than, say, an antiviral drug would?
It doesn't kill the virus or interfere with its internal machinery. It's more like a trap. The virus sticks to the carrageenan before it ever reaches a cell, so the cell never gets infected in the first place. That's why it matters that it's not toxic—you're not poisoning anything, just preventing contact.
And the fact that it worked against COVID-19 in an 80 percent reduction—does that automatically mean it will work as well here?
Not automatically, no. Different viruses have different structures, different ways of entering cells. But both are respiratory viruses, both spread through mucous membranes, and the mechanism—the electrostatic binding—is fundamental enough that it's reasonable to expect some effect. The lab work confirms that expectation, at least in cells.
What's the gap between what they've shown and what would actually help patients?
Everything. They've shown it works in a dish. The next step is a clinical trial—real people, real infection, real outcomes. That takes time, funding, regulatory approval. The cruise ship is a tragedy, but it's also not a controlled experiment. You can't ethically use an outbreak as your trial.
Why hasn't carrageenan been tested against hantavirus before?
Hantavirus is rare, and it's mostly a rural disease in South America. There's less research funding, less institutional attention. COVID-19 changed that calculus—suddenly there was money and urgency to study antivirals. One of these researchers apparently proved years ago that Andes spreads person-to-person, which nobody believed at first. That kind of work doesn't get done unless someone is paying attention.
If they get the funding and run the trial, how long before this could actually be available to patients?
Years, probably. Clinical trials take time. But they have a drug that's already proven safe in thousands of people. That's a huge advantage. They're not starting from scratch.