What is the risk to cattle and humans
While H5 bird flu (H5N1 avian influenza clade 2.3.4.4b) mostly affects birds, it can affect some mammals, including cattle.
Since 2024, H5 bird flu has been detected in dairy cattle in the United States, likely following introduction from infected wild birds. Cases remain rare.
The risk of transmission from cattle to humans is low. A small number of overseas dairy farmworkers who were in close contact with infected cattle and not wearing appropriate PPE were also infected with the virus. These workers showed mild symptoms and recovered.
To date, H5 bird flu has not been detected or reported in beef cattle.
American Veterinary Medical Association advises that most cattle recover in 2 to 3 weeks with supportive care. Farmers can reduce the risk of infection and spread by implementing strong biosecurity measures and limiting cattle exposure to wild birds and contaminated environments.
How H5 bird flu spreads and signs in cattle
H5 bird flu spreads quickly by direct contact, as well as indirectly through bird contact with feed, water, clothing, equipment, materials and surfaces that have been contaminated with the virus. It mostly transfers between birds. However, farmers and vets should be aware of symptoms in cattle.
Signs of H5 bird flu in cattle may include:
- reduced milk production
- thicker colostrum-like milk
- reduced appetite
- lethargy
- fever
- dehydration.
Some infected cattle may not show any clinical signs.
We’ll update this page as new information becomes available, including the latest guidance for farmers on recognising and responding to H5 bird flu.
How to protect your herd
MPI assesses the risk of transmission from birds to cattle or other livestock in New Zealand as very low. One reason for this is that our farming practices are different from the United States. However, we recommend remaining alert, maintaining good biosecurity practices and monitoring the health of your herds.
Recommendations for good biosecurity practices
- Seek veterinary advice if animals become unwell.
- Keep NAIT (National Animal Identification and Tracing) updated. NAIT is a legal requirement and key to good biosecurity, as it makes it easier and faster to trace animals.
- Keep cattle in separate groups and avoid mixing them. Minimise the number of new animals introduced and keep them low risk. For example, keep mobs separate on grazing blocks.
- Secure boundaries through fencing and due diligence. Make sure nose-to-nose contact is not possible between cattle held on neighbouring properties.
- Ensure any biological products and equipment you bring on-farm (such as borrowed milk-feeding equipment) are clean and disinfected prior to use on your property.
- Avoid having staff work across multiple sites unless good decontamination steps are in place for farm gear and equipment.
- Minimise contact with wild birds and their faeces by fencing off waterways, ponds, and duck nesting areas so cattle or other livestock don’t have access to them.
- Protect feed from potential contamination by wild birds, rodents, and other pests.
- Reduce the risk of introduction of any virus or bacteria into the mammary tissue of dairy cattle by maintaining good hygiene practices during milking.
No risk from drinking pasteurised milk
There is no risk to human health from consuming pasteurised milk and milk products from dairy cattle infected with H5 bird flu. Testing in the United States has shown that while non-infectious viral fragments may be detected in pasteurised milk, the pasteurisation process kills the virus.
Health authorities advise against consuming raw (unpasteurised) milk. New Zealand does not import unpasteurised dairy products from the United States.
Report sick or dead wild birds in a group
The most obvious sign of H5 bird flu is sudden death in several birds. Other signs can include weakness, tremors, paralysis, difficulty breathing, lack of coordination, blindness, trembling, and diarrhoea.
If you see 3 or more sick or dead wild birds in a group, report it immediately to the exotic pest and disease hotline on 0800 809 966 from anywhere in New Zealand.
You can also make an online report at report.mpi.govt.nz
If you report online, select the ‘dead or dying wild birds’ option from the dropdown list and then the type of bird you have found.
Do not handle or move the birds.
Provide as much detail as you can, including:
- common name or species of sick or dead bird if known
how many are sick or freshly dead, and the total number of birds present - a GPS reading or other precise location information
- photographs and videos of sick and dead birds.
One of our specialist biosecurity investigators will assess the information and contact you.
How to report suspected bird flu – fact sheet [PDF, 643 KB]
H5 bird flu health and safety guidelines for workplaces
Guidelines for workplace managers and people in New Zealand who work with birds and other animals at risk of avian influenza – including dairy cattle – are available.
They provide advice for at-risk occupational groups – those in contact with potentially infected birds and other animals, their products and contaminated materials, or their environments and habitats.
We encourage you to familiarise yourself with the guidelines and consider what they mean for you or your business.
Avian influenza health and safety guidance for workplaces – Health New Zealand | Te Whatu Ora
More information
2025 Bird flu information for farmers – Factsheet [PDF, 2 MB]
Avian influenza – World Organisation for Animal Health (WOAH)
Updates on Highly Pathogenic Avian Influenza (HPAI) – US Food and Drug Administration (FDA)
Influenza (avian and other zoonotic) – World Health Organization (WHO)