This is Bird Flu Bulletin: Daily H5N1 Update, Monday, October 13, 2025.
Top stories
First, the Centers for Disease Control and Prevention reports seven new confirmed human H5N1 cases among dairy farm workers in California over the past 24 hours. All affected individuals developed mild symptoms and none required hospitalization. These cases bring California’s total to 13 for the year, with the CDC emphasizing that cases remain associated with direct exposure to infected dairy cows, not person-to-person spread. As of today, a national total of 27 confirmed human H5 cases has been reported, up from 20 a day ago. The CDC reiterates that the risk to the general public remains low, though surveillance of exposed workers continues with over 5,100 individuals being monitored for symptoms.
Second, the U.S. Department of Agriculture confirms new H5N1 outbreaks in five commercial poultry flocks and six backyard flocks this week, concentrated in the Midwest and South. Ongoing cases in Minnesota, where two large turkey farms have been affected, highlight the seasonal uptick linked to migratory wild birds, which are spreading the virus regionally. Over the last month, more than 4.4 million birds have been culled as part of control measures, with the USDA stressing the importance of strict biosecurity on farms to contain the virus.
Third, researchers announced promising laboratory findings: a study published in Science Translational Medicine shows existing replicating RNA vaccines, based on older H5N1 strains, can protect animals against the latest variants. This suggests that current stockpiled vaccines might offer some level of protection for humans if future needs arise. However, experts warn that the virus continues to evolve, and so far there is no evidence of major genetic changes increasing its ability to infect or spread between people.
Case numbers
Compared to Sunday, confirmed human H5N1 infections have increased from 20 to 27 nationwide, driven by new cases among dairy workers in California, according to the CDC. On the animal side, the number of affected poultry flocks continues to rise, especially as fall migration intensifies viral transmission.
Official guidance
The CDC and USDA again urge poultry and dairy workers to wear personal protective equipment and report flu-like symptoms promptly. The CDC notes that so far, all California cases have been mild, and genetic testing shows no signs of mutations linked to increased human transmissibility or resistance to antiviral medication.
Expert interview
For insight, here’s Dr Jennifer Nuzzo, professor of epidemiology at Brown University, speaking to The Independent: The major worry is that the virus could mutate or recombine, potentially making human-to-human spread easier. At this stage, H5N1 remains largely a bird virus, but any shift could spark a new pandemic. For now, she emphasizes vigilance and ongoing surveillance as essential safeguards.
Looking ahead
Tomorrow, public health authorities expect to release full genomic results for the latest California cases to monitor for any viral changes. Field teams from the CDC will continue deploying to impacted regions, supporting active case finding, farm worker education, and expanded animal testing. The situation is expected to evolve rapidly as the fall migration peaks, and updates on vaccine stockpiles and containment efforts are anticipated.
Thank you for tuning in to Bird Flu Bulletin: Daily H5N1 Update. Join us next week for more. This has been a Quiet Please production. For more, check out Quiet Please dot A I.
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