While much of the global focus has been on the H5N1 outbreak in U.S. dairy cattle, new reports from around the world reveal the virus is actively spreading, evolving, and breaching new boundaries. Recent research has confirmed that infectious virus is present in the air and wastewater of U.S. dairy farms, suggesting new transmission risks for both animals and people. Simultaneously, an uptick in cases in the UK, new human infections in Cambodia, and the detection of new strains in Arctic foxes show that this is a truly global and unpredictable threat.
Cambodia Confirms 15th Human H5N1 Case of 2025, Marking 47% Fatality Rate
Cambodia’s Ministry of Health has confirmed its 15th human H5N1 case of the year, involving a 6-year-old girl from Takeo province who is hospitalized with fever, cough, and breathing difficulty. The case was confirmed by Cambodia’s National Institute of Public Health and linked to extensive poultry die-offs in the child’s village—nearly 1,000 sick or dead chickens over the past month, including 30 at her home. Her mother reportedly cooked several of the dead birds shortly before the child fell ill. According to Erik Karlsson of Cambodia’s Pasteur Institute, 7 of the 15 cases this year have been fatal, resulting in a case-fatality rate of 46.6%. Most recent infections involve a reassortant virus combining the long-circulating 2.3.2.1e clade with the globally dominant 2.3.4.4b strain. The pace of cases has accelerated, with 12 reported in the past two months alone (Schnirring, 2025).
Live H5N1 Virus Found in Air and Wastewater on Dairy Farms, Exposing New Transmission Risks
New research led by Emory University and posted to bioRxiv confirms that infectious H5N1 virus is present in the air and wastewater of U.S. dairy farms, particularly in milking parlors. Scientists detected viral RNA in 21 of 35 air samples across 14 outbreak-linked farms in California, with live virus found in 4 samples. Notably, one sample came from a device worn to model human exposure, suggesting workers may inhale the virus during milking. Researchers also isolated infectious virus from two wastewater samples taken from farm drains and manure lagoons, sites that attract migratory birds and serve as potential environmental reservoirs. “These results demonstrate that H5N1 is prevalent in reclaimed farm wastewater sites across dairy farms and may serve as another source of H5N1 spread between cows, to humans, and to peri-domestic animals,” the team wrote. The virus appears to aerosolize from contaminated milk during the milking process. “There’s tons of aerosols being generated,” said Dr. Seema Lakdawala, the study’s lead author (Apoorva Mandavilli & Anthes, 2025). Though some breath samples from cows contained viral RNA, none showed infectious virus—suggesting airborne virus likely originates from milk droplets, not respiration. The study also found subclinical infections in cows, signaling silent viral spread. Milking parlors, which are hot, humid, and poorly ventilated, were identified as high-risk zones. As of August 15th, 2025, 1,078 U.S. dairy herds have tested positive, with 771 in California alone (Schnirring, 2025).
Summer Surge of H5N1 Detected in UK Commercial Poultry
The United Kingdom has reported 10 H5N1 avian flu outbreaks in commercial poultry over the past two weeks, an unusual summer uptick following a five-week lull and lowered threat level. The latest detections occurred on farms in East and West Devon. This marks a shift from last year’s pattern, when no poultry outbreaks were reported between March and early April. While experts caution the trend could be temporary, the recurrence during summer months deviates from typical seasonal behavior. Ireland also reported an H5N1 outbreak in a backyard flock on July 31 (Schnirring, 2025).
China Bans Spanish Poultry Imports Following Basque Region H5 Outbreak
China has imposed a ban on poultry and related product imports from Spain following the confirmation of an avian influenza outbreak in Spain’s northern Basque region on August 4. The measure was announced by China’s customs administration in a notice dated August 7. Spain’s agriculture ministry stated the ban has no immediate trade impact, as poultry exports to China had not yet commenced. An export protocol for products such as turkey and chicken feet was signed in April, but applications were still under review at the time of the ban. Spanish authorities are working with the World Organisation for Animal Health to control the outbreak and lift restrictions (Reuters Staff, 2025).
Thailand Heightens Bird Flu Surveillance Amid Ongoing Cambodia Spread
In response to the recent H5N1 outbreaks in Cambodia’s Siem Reap province, the Thai government has intensified biosecurity measures and surveillance along its eastern border. Specifically, officials are monitoring Sa Kaeo and Buri Ram provinces. As previously stated above, seven of Cambodia’s 15 cases this year have been fatal (Schnirring, 2025b). Authorities are urging poultry farmers to follow strict hygiene measures, disinfect vehicles entering farms, and report any unexplained bird deaths (Nation Thailand, 2025).
H5N5 Avian Influenza Detected in Arctic Foxes in Svalbard, First Cases in Norway
The Norwegian Veterinary Institute has confirmed highly pathogenic avian influenza (HPAI) in four arctic fox pups near Barentsburg, marking the first known HPAI infections in arctic foxes in Norway. All four tested positive for the H5N5 subtype, which is known to circulate in the high north and was previously detected in a walrus in Svalbard in 2023. The infected pups were part of a larger group of six foxes euthanized in late July due to illness and proximity to a human settlement. Tests ruled out rabies, but the neurological symptoms observed—such as circling, head tilt, and reduced fear of humans—are consistent with HPAI brain infection. Foxes are likely exposed to the virus through scavenging infected birds, but studies suggest they do not transmit the virus to each other. (Governor of Svalbard, 2025).
The latest developments in the H5N1 outbreak underscore a critical point: while media attention may fluctuate, the virus's spread and evolution do not. The discovery of H5N1 in dairy farm air and wastewater, coupled with a summer surge in the UK and cross-species infections in Arctic foxes, highlights the virus's adaptability and the pervasive nature of its presence. As authorities in Cambodia and Thailand work to contain human cases, the global picture remains one of vigilance. This continued spread serves as a powerful reminder that proactive surveillance and international cooperation are essential to managing a virus that is far from contained.
References
Apoorva Mandavilli, & Anthes, E. (2025, August 4). Bird Flu May Be Airborne on Dairy Farms, Scientists Report. The New York Times. https://www.nytimes.com/2025/08/04/health/bird-flu-airborne.html
Governor of Svalbard. (2025). Avian influenza detected in arctic foxes in Svalbard. Governor of Svalbard. https://www.sysselmesteren.no/en/news/2025/08/avian-influenza-detected-in-arctic-foxes-in-svalbard/
Nation Thailand. (2025, August 4). Govt steps up surveillance against H5N1 bird flu after outbreak in Cambodia. Nationthailand; null. https://www.nationthailand.com/health-wellness/40053554
Reuters Staff. (2025, August 11). China bans Spanish poultry imports due to bird flu. Reuters. https://www.reuters.com/business/healthcare-pharmaceuticals/china-bans-spanish-poultry-imports-due-bird-flu-2025-08-11/
Schnirring, L. (2025a, August 4). Center for Infectious Disease Research and Policy. CIDRAP. https://www.cidrap.umn.edu/avian-influenza-bird-flu/air-wastewater-may-play-roles-h5n1-transmission-dairy-farms
Schnirring, L. (2025b, August 6). Center for Infectious Disease Research and Policy. Umn.edu. https://www.cidrap.umn.edu/avian-influenza-bird-flu/cambodia-announces-15th-human-h5n1-infection-year
Schnirring, L. (2025c, August 11). Center for Infectious Disease Research and Policy. Umn.edu. https://www.cidrap.umn.edu/avian-influenza-bird-flu/h5n1-avian-flu-detections-pick-uk-poultry