May 18, 2026

expert reaction to latest UKHSA hantavirus update including receiving from Japan doses of the antiviral medicine favipiravir (FAVI)

Scientists comment on the latest Hantavirus update from the UK Health Security Agency (UKHSA) on receiving doses of the antiviral favipiravir (FAVI).

Prof Piet Maes, President-elect of the Hantavirus Society, and Virologist at the Plotkin Institute, University of Brussels, said:

What is favipiravir?

“Favipiravir is a broad-spectrum antiviral drug that inhibits the viral RNA-dependent RNA polymerase, an enzyme required for replication of many RNA viruses.  It was originally developed for influenza and has since been investigated experimentally against several emerging RNA viruses, including Ebola virus, Lassa virus, and hantaviruses.

How is favipiravir administered, and under what circumstances would it be given?

“Favipiravir is administered orally.  In the context of hantavirus infections, its use would generally be considered experimental or compassionate rather than standard-of-care.  It would most likely be considered early in the course of disease, particularly in severe infections such as Andes virus infection, where mortality can be high and therapeutic options remain limited.  However, there is currently no internationally established clinical protocol recommending favipiravir as a routine treatment for hantavirus disease.

What is the evidence that it helps as a treatment for hantavirus?

“The evidence remains limited.  Favipiravir has shown antiviral activity against hantaviruses in vitro in laboratory studies and in vivo in an animal model (a lethal hamster model mimicking the human Andes virus disease).  However, there are currently no robust randomized clinical trials demonstrating clear benefit in humans with hantavirus disease.

“This is important because antiviral drugs that appear promising in vitro or in animal studies do not always translate into meaningful clinical benefit in humans.  During the 2014–2016 Ebola outbreak, favipiravir also generated considerable early optimism based on experimental data, but subsequent clinical studies showed more limited benefit than initially hoped.

“At present, favipiravir should therefore still be regarded as an investigational treatment for hantavirus infection rather than a proven therapy.  Further controlled clinical studies would be needed to determine whether it provides significant benefit, particularly regarding timing of administration, disease severity, and optimal dosing.”

https://www.gov.uk/government/news/ukhsa-update-on-the-hantavirus-cruise-ship-outbreak

All our previous output on this hantavirus cluster can be seen at these links:

https://www.sciencemediacentre.org/expert-reaction-to-latest-hantavirus-update-from-the-ukhsa-including-that-six-individuals-from-arrowe-park-are-returning-home-or-to-other-accommodation-to-complete-their-45-day-isolation-period/

https://www.sciencemediacentre.org/expert-reaction-to-media-reports-that-a-french-and-an-american-mv-hondius-passenger-have-developed-symptoms-and-or-tested-positive-for-hantavirus-since-being-transported-back-to-their-home-countries/;

https://www.sciencemediacentre.org/expert-reaction-to-current-hantavirus-situation-as-passengers-on-the-mv-hondius-are-taken-off-in-stages-and-taken-onwards-to-their-countries-of-origin/;

https://www.sciencemediacentre.org/expert-reaction-to-first-complete-sequence-of-the-hantavirus-from-the-current-cluster-from-mv-hondius-from-the-swiss-patient-with-confirmed-andes-strain-uploaded-to-the-virological-org-platform-by-t/;

https://www.sciencemediacentre.org/expert-reaction-to-statement-from-the-ukhsa-dhsc-and-fcdo-re-hantavirus-including-transport-arrangements-and-isolation-for-british-passengers-and-crew-aboard-the-mv-hondius/;

https://www.sciencemediacentre.org/expert-reaction-to-hantavirus-update-from-the-ukhsa-including-that-two-people-had-returned-to-the-uk-having-been-on-board-the-mv-hondius-are-not-currently-reporting-symptoms-and-are-self-isolating/;

https://www.sciencemediacentre.org/expert-reaction-to-continuing-hantavirus-situation-aboard-cruise-ship/;

https://www.sciencemediacentre.org/expert-reaction-to-hantavirus-situation-on-cruise-ship-heading-from-argentina-to-cape-verde/

Declared interests

Prof Piet Maes: “I have no interests to declare.”