What You Need To Know About Bird Flu in Dairy Herds

Bird flu affects cow health, lowers milk production, and has the potential to spread between herds. USDA and other Federal, State, and industry partners are working together to fight these outbreaks, support producers, and improve prevention efforts. APHIS has resources to help producers “Secure Their Herds” at www.aphis.usda.gov/secureourherds.

In dairy cattle, bird flu primarily spreads through the movement of cattle and normal farm operations like sharing vehicles and equipment, milk handling, and people moving between farms. So far, there’s no evidence that wild birds are the main source of cattle infections.

Dairy cows infected with bird flu often show mild to moderate clinical signs. Common signs may include: 

• Lower milk output 
• Thicker, colostrum-like or highly concentrated milk 
• Reduced appetite or feed intake 
• Abnormal feces (tacky or loose) 
• Lethargy 
• Fever 
• Dehydration 

Most herds see less than 10–20 percent of cows get sick, and death rates are usually under 2 percent. If you see any of these signs, isolate the sick animal(s) and report them to your veterinarian and/or State and Federal animal health officials.

You can help protect your herd and other animals from bird flu by taking steps to keep diseases from reaching your animals. Even small changes in daily routines can make a big difference in keeping your herd safe. 

• Keep your herds healthy with proper care, ensuring they have clean water, nutritious food, and clean bedding. 
• Stop germs from spreading by limiting visitors and not sharing equipment, spraying disinfectants on all vehicle and trailer tires before entering the farm, and keeping a separate pair of boots and coveralls for use on the farm around your animals. 
• Separate different species and keep other animals, including pets and wildlife, away from your livestock areas. 
• Be extra careful when you travel. Biosecurity is especially important at fairs and exhibitions. Limit contact with other exhibitors’ animals, follow the event’s biosecurity plan, and use a checklist to help you stay prepared. 
• Create a plan that includes these practices now. A plan makes biosecurity an everyday activity for staff and everyone who visits or travels between farms—such as milk haulers, veterinarians, and feed suppliers. Complete regular walkthroughs and update your plan as needed.

The first detections occurred in March 2024, when unpasteurized milk samples from sick cattle on dairies in Kansas and Texas tested positive for the virus. Because bird flu is highly transmissible, it spread quickly to other herds. USDA APHIS provides an interactive map and data showing new livestock cases reported in the last 30 days, along with total confirmed cases by State, updated each weekday.

In April and December 2024, USDA issued Federal Orders requiring testing of lactating dairy cattle before they move across State lines, testing of raw milk intended for pasteurization, and mandatory reporting of any positive test results. The voluntary Dairy Herd Status Program allows producers to monitor herds using weekly bulk tank milk samples instead of individual testing. The National Milk Testing Strategy, rolled out with a Federal Order in December 2024, requires testing of unpasteurized milk on a national scale to track virus presence.

USDA offers financial support to dairy herd producers, including those affected and unaffected by bird flu. This financial support helps producers enhance biosecurity practices, offset costs associated with testing and shipping samples, and protect their employees.

For ongoing updates, comprehensive information, guidance, and free resources on bird flu in dairy herds, visit the USDA Secure Our Herds website at www.aphis.usda.gov/secureourherds.