Two new studies released in 2025 provide a mixed picture of how well our today’s antivirals hold against H5N1, the very pathogenic virus of bird flu that continues to mammail in mammals and humans. The good news: H5N1 viruses from recent human cases remain sensitive to early antiviral drugs. More concerns a mutation of resistance that emerged and spread rapidly during a poultry epidemic in Canada, increasing the flags on the virus’s ability to evolve beyond our defenses.
Oseltamivir antiviral (commonly known as Tamiflu) is currently Recommended to treat and prevent H5N1 infections. It works by inhibiting neurminidase, a surface protein used by the virus to release from infected cells and spread through the body. But this treatment only works if the virus remains sensitive to the drug.
The latest studies
Tamiflu, the same antiviral used to treat ordinary seasonal influenza, is the first -line drug … more
To one study Published in CDC Magazine Emerging infectious diseasesThe researchers examined H5N1 viruses from human infections reported in Cambodia, Chile and the United States during 2023-2024. These viruses belonged to two clades: 2.3.2.1c and 2.3.4.4b. All tested viruses were sensitive to Oseltamivir and other neuralidase inhibitors, including Zanamivir and Peramivir, as well as Baloxavir, a younger drug aimed at different viral protein. Most also remained sensitive to earlier anti-bloody M2-except for two viruses isolated in Cambodia. These results support the continuation of the use of Oseltamivir as a first -line treatment and to protect after exposure to close contacts of infected people.
The computer created 3D model, showing a cross section of RNP green spirals, blue hemoglitine, … more
However, not all recent developments are reassuring. Distinctive study published Popups and infections He documented a large outbreak of H5N1 in poultry in British Colombia, Canada. The genetic sequence of the virus revealed the presence of the H275Y mutation in the neurminidase-known gene known to give Oseltamivir resistance. This mutation had previously rendered the majority of seasonal viruses H1N1 drug -resistant During the 2008-2009 influenza era.
What makes the Canadian case remarkable is how quickly the resistant virus spreads. Within 27 days of detection, it had jumped to 44 farms. While resistance mutations such as the H275Y are often associated with reduced viral capacity, the Canadian epidemic strain quickly spread between the holdings, suggesting that this particular virus was able to transmit effectively despite the transfer of the mutation. The mutation seems to have emerged through redesign, a process of genetic mixing that occurs when the influenza viruses exchange sections. In this case, the virus acquired the section of neurminidase from a different flu genealogy circulating in birds in North America.
We need to manage H5N1 epidemic
These findings illustrate how resistance to animal populations can occur, long before human homes begin. They also emphasize the importance of genomic monitoring – not only in humans but also in poultry and wild birds, where the virus continues to evolve.
Combination treatments can offer a way of slowing resistance. Animal studies have shown that the use of multiple drugs with different mechanisms at the same time can more effectively reduce viral load and reduce the chances of endurance. But in the real world, access to such treatments remains limited.
At the moment, Tamiflu still works – but the virus changes. Our answer must keep the pace.
