High Pathogenicity Avian Influenza (HPAI)

HPAI and the risk to New Zealand dairy cattle

HPAI is not typically a cattle disease, but H5N1 2.3.4.4b has infected dairy cows in the United States (US). Antibodies indicating past exposure were also detected in some dairy cattle in the Netherlands in early 2026, although no active virus, clinical outbreak or onward spread was confirmed. Although H5N1 has now been detected in New Zealand, the risk of spillover to dairy cattle is still considered low.

A different HPAI strain, H7N6 was identified on a poultry farm in Otago in 2024 and was effectively contained to a single property. This strain is only known to infect bird species in the countries where it is already present.

Genomic evidence from the United States suggests H5N1 has entered dairy cattle through two separate spillover events from wild birds. While this shows spillover can occur, it appears to remain uncommon worldwide. In the US, the main dairy cattle outbreak has spread largely through cattle movements and other farm-to-farm transmission pathways after the virus entered cattle. This means reducing the chance of farm-to-farm spread remains important, and the risk of H5N1 spilling over into New Zealand dairy cattle is still considered low.

In the United States, infected cows generally have had mild symptoms, resulting in a period of decreased milk production, decreased appetite, fever and dehydration. The majority of infected cows recover in 2-3 weeks with supportive care. Not all cows in a herd become sick if infected.

Pasteurisation of milk kills H5N1. In the event of a New Zealand outbreak, pasteurised milk would be safe to consume.

There have been no cases to date of HPAI in beef cattle.

HPAI has killed millions of birds worldwide and continues to affect wild birds, poultry and some mammals overseas. In New Zealand, the immediate concern is for poultry and native birdlife. While the risk to dairy cattle remains low, dairy farmers have an important role in reducing contact between birds and cattle, protecting feed and water sources, and reporting unusual illness or mortality in wildlife.

What actions can farmers take?

We cannot prevent infected migratory birds from reaching New Zealand, but good biosecurity can help reduce the chance of the virus spreading to poultry, livestock or other wildlife.

Implications for human health

Human infection is rare and generally associated with close or prolonged contact with infected birds or other infected animals.

In the US, H5N1 has been detected in some people who had close contact with infected cattle or poultry. US authorities have also highlighted unpasteurised raw milk as a possible route of exposure, so people should avoid drinking raw milk or consuming products made from raw milk. Livestock farmers, workers and rural professionals should avoid unprotected direct physical contact or close exposure to animals, raw milk, or other materials that could be infected or confirmed to be infected with H5N1.

To date, human-to-human transmission has not been reported.

What is DairyNZ doing to prepare for HPAI?

Biosecurity New Zealand will lead the response with support from the Department of Conservation (DOC), the Ministry of Health (MoH) and Health New Zealand (Te Whatu Ora).

DairyNZ is working with the Ministry for Primary Industries (MPI) and industry partners to stay informed on HPAI developments, understand any changes to risk for dairy farmers, and support clear, practical guidance for the sector.

Helpful information

• High pathogenicity avian influenza and the risk to NZ - MPI
• Don't let bird flu take flight - MPI
• Bird Flu Biosecurity Aotearoa - a poultry industry initiative
• Avian influenza – World Organisation for Animal Health
• Department of Conservation – Avian influenza