While the U.S. has experienced a lull in H5N1 cases, new reports from around the world show the virus continues to evolve, spread, and cause significant harm. The USDA is paying out hundreds of millions of dollars to aid U.S. farms, while other countries are grappling with the virus spilling into new animal species and claiming more human lives. Recent studies offer hope with new vaccines and antivirals, but also warn that the virus is finding new ways to transmit, underscoring the ongoing threat.
USDA Issues $230 Million In Relief To California Dairies Devastated By H5N1
The USDA has paid out over $230 million to California dairy farms hit by H5N1 bird flu, which has affected more than 75% of the state’s 1,000 dairies since August 2024. Under the Emergency Assistance for Livestock Program (ELAP), 359 farms received 644 payments between November 2024 and June 2025, with payouts ranging from $2,058 to $4.4 million and averaging $645,000 per farm. The outbreak has caused major milk production losses and widespread cattle deaths, with each dead cow representing an estimated $3,500 loss. Farmers report expenses far exceeding compensation, including lost milk income and soaring care costs. Western United Dairies CEO Anja Raudabaugh said the funds have been “critical” for keeping operations afloat as producers await approval of a cattle vaccine (Rust, 2025).
Cambodia Confirms 14th Human H5N1 Case This Year
A 26-year-old man from Siem Reap province has been hospitalized in intensive care with H5N1 following exposure to sick and dead chickens he slaughtered three days earlier. The case, confirmed on July 26, brings Cambodia’s 2025 total to 14 human infections, 7 of which have been fatal—a 50% mortality rate. Since 2005, Cambodia has recorded 86 H5N1 cases and 50 deaths, a case-fatality rate of 58.1%. Most recent infections involve a reassortant virus (clade 2.3.2.1e) combining a long-circulating Cambodian strain with the globally dominant 2.3.4.4b clade. Health officials are distributing oseltamivir and conducting contact tracing. UN agencies say the global risk remains low, but warn of elevated danger for individuals with frequent animal exposure (Schnirring, 2025).
Early Antiviral Treatment Crucial Against H5N1 Cattle Strain, Study Finds
A Japanese study published in Nature Communications found that the antiviral drug baloxavir marboxil can fully protect against the H5N1 bird flu strain spreading in U.S. dairy cattle—but only if administered quickly. Mice treated within one hour of infection showed 100% survival and no detectable virus. Delaying treatment to 24 hours led to 60% mortality, while treatment after 48 hours failed completely. Late intervention also increased the risk of drug-resistant variants carrying the PA-I38T mutation, which reduced the drug’s effectiveness by up to 136-fold (Kiso et al., 2025).
India Reports Bird Flu In 10 States With Infections In Tigers, Lions, And Cats
India has reported 41 cases of bird flu in animals across 10 states as of July 24, 2025, with no confirmed human infections, according to a July 30 statement from Union Minister S. P. Singh Baghel. The affected states include Maharashtra, Uttar Pradesh, Andhra Pradesh, and others. Notably, the virus has spilled over from birds into several mammal species, including tigers, lions, leopards, jungle cats, and domestic cats, raising concern over unusual cross-species transmission. In response, India has deployed Rapid Response Teams, issued advisories for the winter migration season, and implemented an AI-powered early warning system that predicts outbreaks up to two months in advance. The government has approved an H9N2 poultry vaccine and is offering financial support for culling under the Assistance to States for Control of Animal Diseases (ASCAD) scheme. Although India reported one unrelated human death from H5N1 earlier this year, no human infections have been linked to the current outbreaks in animals (MSN, 2025).
China Reports Two New Human H9N2 Cases, Bringing 2025 Total To 18
China has confirmed two additional human infections with H9N2 avian influenza—one in Guangdong province (late May onset) and another in Hubei province (mid-June), according to Hong Kong’s Centre for Health Protection. Patient ages were not disclosed, but prior 2025 data show that children account for the majority of cases: 11 of the 16 previously reported were 18 years old or younger. All 18 confirmed H9N2 cases this year have occurred in mainland China, with Hunan province reporting the highest number (six). H9N2 infections are typically linked to contact with infected poultry. For comparison, China reported 11 total cases in 2024 (Soucheray, 2025).
Past H1N1 Infection May Help Protect Humans From Deadly H5N1 Bird Flu
A July 23 study in Science Translational Medicine found that prior infection with the 2009 H1N1 pandemic flu strain significantly protected ferrets from severe disease and death after H5N1 exposure. Researchers from Penn State and the University of Pittsburgh showed that H1N1-immune ferrets developed cross-reactive antibodies against H5N1’s neuraminidase protein, had lower viral shedding, and survived lethal challenges with H5N1 strains from both mink and cattle. In contrast, all naive ferrets died after direct contact. Seasonal H3N2 immunity offered some protection, but less than H1N1. The findings suggest prior H1N1 exposure may help explain why most recent human H5N1 cases have been mild, pointing to potential population-level resilience (Restori et al., 2025).
Duke Vaccines Provide Complete Protection In Mice Against Deadly Texas H5N1 Strain
Researchers at Duke University have developed DNA and mRNA vaccines that provided complete protection in mice against the H5N1 bird flu strain linked to a Texas dairy worker case from March 2024. Published in the Journal of Virology, the study used a dual-antigen design combining hemagglutinin (HA) and neuraminidase (NA) proteins from the A/Texas/37/2024 strain in a single genetic sequence, which enhanced immune response and simplified production. Vaccinated mice showed no signs of illness after lethal exposure, while all unvaccinated controls died within five days. The vaccines also suppressed viral load in the lungs and reduced inflammation markers. These findings offer a potential roadmap and tool if the vaccination of livestock becomes necessary (Leonard et al., 2025).
Flies And “Milk Snatching” Emerge As Possible H5N1 Vectors In Dairy Cattle
New research highlights overlooked H5N1 transmission routes in cattle: house flies and mouth-to-teat contact. A genetic sequence from a California house fly matched the B3.13 strain seen in infected cows, raising concerns about mechanical transmission via contaminated limbs. Though flies aren’t biologically infected, experts say they may carry virus particles between animals (Schnirring, 2025). Meanwhile, a Chinese study in National Science Review found H5N1 replicated in mammary glands only when introduced via the teat—suggesting that “milk snatching,” where cows or calves nurse from multiple animals, creates a direct pathway for infection and may play a significant role in herd-level spread (Shi et al., 2025).
H5N1 In Dairy Cattle Still Avian In Nature, Poses Low Airborne Risk To Humans
A July 23 study from St. Jude Children’s Research Hospital, published in Nature Communications, finds that the H5N1 virus circulating in U.S. dairy cattle retains key avian characteristics, limiting its ability to spread through the air between humans. The virus binds more effectively to bird cell receptors than to mammalian ones and failed to transmit via air in mammalian models. While direct transmission remains a concern—41 human cases have been linked to close contact with infected cattle—researchers found no evidence of antiviral resistance (St. Jude Children's Research Hospital, 2025).
Spain Reports Deadly H5N1 Outbreak On Turkey Farm
Spain has confirmed an H5N1 avian influenza outbreak on a turkey farm in Extremadura, according to the World Organisation for Animal Health (WOAH). The outbreak killed nearly the entire flock of 6,895 birds; the 10 survivors were culled as a precaution (Reuters, 2025).
Bird Flu Outbreak Hits UK Commercial Poultry Farms, Thousands Of Birds Culled
Bird flu has been confirmed at multiple sites in southwest England, including a commercial poultry farm near Tiverton in Devon, triggering mass culling and containment measures. According to the UK Department for Environment, Food and Rural Affairs (DEFRA), all birds at the affected Tiverton site will be humanely culled. Additional outbreaks were reported near Minehead and Winsford, where 2,500 pheasant chicks are also set to be culled. Protection and surveillance zones of 3km and 10km have been declared. An Avian Influenza Prevention Zone remains in effect across England, Scotland, and Wales, applying to both commercial and backyard flocks (Young, 2025).
Novavax H5N1 Vaccine Shows Single-Dose Protection In Primate Trials
Novavax has developed an H5N1 bird flu vaccine using their Matrix-M nanoparticle technology that showed strong results in animal studies. Published in Nature Communications, the vaccine targets the clade 2.3.4.4b strain currently spreading in U.S. dairy cattle and infecting farm workers. In nonhuman primates with prior seasonal flu vaccination, a single intramuscular shot produced protective antibody levels above the standard threshold, while nasal spray delivery required two doses. The vaccine also worked well in mice through both injection and nasal routes. Testing showed the vaccine generates broad immune responses against multiple H5N1 variants, suggesting it could protect against different strains of the virus. This represents a significant advancement, as many vaccines require multiple doses for complete protection (Patel et al., 2025).
Machine Learning Model Forecasts European Bird Flu Outbreaks With High Accuracy
A July 17 study in Scientific Reports found that a new machine learning model can predict highly pathogenic avian influenza (HPAI) outbreaks in Europe with up to 94% accuracy. Built by European researchers, the model analyzed 15 years of outbreak data alongside climate, land, and poultry industry variables across hundreds of local regions. It identified cold fall temperatures, high poultry density, and water and vegetation levels as key risk factors. Mute swans were flagged as the wild bird species most likely to spread HPAI to poultry. When tested on real outbreaks from 2022–2023, the model accurately predicted 88% of them, showing strong potential as an early warning tool for farms and policymakers (Opata et al., 2025).
Nasal Flu Vaccine Shows Protection Against H5N1 In Mice
Mount Sinai researchers have developed a nasal spray flu vaccine that offers broad protection, including partial defense against the H5N1 bird flu strain circulating in U.S. dairy cattle. Published in npj Vaccines, the study showed that mice receiving the intranasal vaccine were fully protected from seasonal flu and partially protected from H5N1. The nasal route generated strong local immune responses in the respiratory tract, where flu viruses typically enter, triggering robust antibody production and immune cell activation. Researchers say this platform could provide broader and more adaptable protection against both seasonal and emerging flu threats, including potential pandemics (Vasilev et al., 2025).
The latest developments in the H5N1 outbreak present a mixed picture. While researchers are making progress on new vaccines and treatments, the virus is simultaneously demonstrating a concerning ability to adapt and spread globally. The financial fallout in the U.S. and the rising human case count in other regions serve as a reminder that the H5N1 threat is far from over. Ongoing research and international collaboration are vital to stay ahead of a virus that continues to surprise us with its resilience.
References
Kiso, M., Uraki, R., Yamayoshi, S., & Kawaoka, Y. (2025). Efficacy of baloxavir marboxil against bovine H5N1 virus in mice. Nature Communications, 16(1). https://doi.org/10.1038/s41467-025-60791-5
Leonard, R. A., Spurrier, M. A., Skavicus, S., Luo, Z., Heaton, B. E., Spreng, R. L., Hong, J., Yuan, F., & Heaton, N. S. (2025). Development of DNA and mRNA-LNP vaccines against an H5N1 clade 2.3.4.4b influenza virus. Journal of Virology. https://doi.org/10.1128/jvi.00795-25
MSN. (2025). MSN. Msn.com. https://www.msn.com/en-in/health/health-news/bird-flu-cases-reported-in-10-states-govt-confirms-infections-in-tiger-lion-leopard-and-cats/ar-AA1JB576
Opata, M. R., Lavarello-Schettini, A., Semenza, J. C., & Rocklöv, J. (2025). Predictiveness and drivers of highly pathogenic avian influenza outbreaks in Europe. Scientific Reports, 15(1), 1–12. https://doi.org/10.1038/s41598-025-04624-x
Patel, N., Rehman, A., Trost, J. F., Flores, R., Longacre, Z., Guebre-Xabier, M., Zhou, H., Zhou, B., Jacobson, K., Jiang, D., Bai, X., Khatoon, R., Kort, T., Norton, J., M Madhangi, Hersey, M., Greene, A. M., Dubovsky, F., & Smith, G. (2025). Single-dose avian influenza A(H5N1) Clade 2.3.4.4b hemagglutinin-Matrix-M. PubMed, 16(1), 6625–6625. https://doi.org/10.1038/s41467-025-61964-y
Restori, K. H., Weaver, V., Patel, D. R., Merrbach, G. A., Septer, K. M., Field, C. J., Bernabe, M. J., Kronthal, E. M., Minns, A., Lindner, S. E., Lakdawala, S. S., Le Sage, V., & Sutton, T. C. (2025). Preexisting immunity to the 2009 pandemic H1N1 virus reduces susceptibility to H5N1 infection and disease in ferrets. Science Translational Medicine, 17(808). https://doi.org/10.1126/scitranslmed.adw4856
Reuters. (2025, July 18). Spain reports bird flu outbreak on turkey farm. Reuters. https://www.reuters.com/business/healthcare-pharmaceuticals/spain-reports-bird-flu-outbreak-turkey-farm-2025-07-18/
Rust, S. (2025, July 28). California dairy farmers got millions to cover bird flu losses. Critics say that’s part of the problem. Los Angeles Times. https://www.latimes.com/science/story/2025-07-28/ca-dairies-cash-in-on-usda-bird-flu-indemnity-payouts-220-million
Schnirring, L. (2025a, July 18). Center for Infectious Disease Research and Policy. CIDRAP. https://www.cidrap.umn.edu/avian-influenza-bird-flu/flies-milk-snatching-among-h5n1-transmission-contributors-dairy-cattle
Schnirring, L. (2025b, July 29). Center for Infectious Disease Research and Policy. CIDRAP. https://www.cidrap.umn.edu/avian-influenza-bird-flu/h5n1-avian-flu-hospitalizes-cambodian-man
Shi, J., Kong, H., Cui, P., Deng, G., Zeng, X., Jiang, Y., He, X., Zhang, X., Chen, L., Zhuang, Y., Wang, Y., Ma, J., Li, J., Zhang, Y., Wang, C., He, C., Yang, J., Li, J., Liu, W., & Yang, J. (2025). H5N1 virus invades the mammary glands of dairy cattle through “mouth-to-teat” transmission. National Science Review. https://doi.org/10.1093/nsr/nwaf262
Soucheray, S. (2025, July 22). Center for Infectious Disease Research and Policy. Umn.edu. https://www.cidrap.umn.edu/avian-influenza-bird-flu/china-reports-more-h9n2-activity
St. Jude Children's Research Hospital. (2025). H5N1 found in dairy cattle retains preference for infecting birds, representing low risk to humans. Stjude.org. https://www.stjude.org/media-resources/news-releases/2025-medicine-science-news/h5n1-found-in-dairy-cattle-retains-preference-for-infecting-birds.html
Vasilev, K., Hoxie, I., Eduard Puente-Massaguer, Yueh, J., Bhavsar, D., Singh, M., Mallett, C. P., Zimmermann, J., & Krammer, F. (2025). Immunogenicity and protective efficacy of an intranasal neuraminidase-based influenza vaccine with bacterial cell membrane-derived adjuvants. Npj Vaccines, 10(1). https://doi.org/10.1038/s41541-025-01209-7
Young, L. (2025, July 31). Bird flu confirmed at commercial poultry farm near Tiverton. BBC. https://www.bbc.com/news/articles/c1jn0r51dy3o