About avian influenza and the risk to NZ

Monitoring avian influenza

Avian influenza (also known as bird flu) is a viral disease that mainly affects domesticated and wild birds. However, it is known to be transmissible to mammals.

New Zealand does not have high pathogenicity avian influenza (HPAI). We are monitoring the spread of this disease globally, particularly towards the Ross Sea region in Antarctica. We’re talking regularly with colleagues around the world so we learn as much as we can about how the disease is behaving as it spreads, and what other countries are doing to manage the disease.

Avian influenza has 2 categories

There are many strains of the avian influenza virus, and 2 categories of virus:

• low pathogenicity avian influenza (LPAI), which typically causes few or no signs in birds but can possibly mutate to become HPAI
• high pathogenicity avian influenza (HPAI), which can cause severe signs and high death rates in birds.

LPAI viruses exist in wild birds and have been detected in New Zealand. Biosecurity New Zealand has an active surveillance programme for LPAI and tests around 2,000 samples from wild birds each year. 

New Zealand has never had HPAI.

Global spread of HPAI H5N1

Strains of HPAI have been circulating globally for many years, with many countries having seasonal outbreaks in poultry every year.

In 2020, a new H5N1 strain of the virus emerged in both domesticated and wild birds across the northern hemisphere. It established in wild birds and began to spread, including to the United Kingdom, Europe, and the United States.

In 2023, H5N1 was detected in the southern hemisphere. Since then, it has spread down through South America to the sub-Antarctic islands and the Antarctic peninsula near South America.   

This H5N1 strain differs significantly from other HPAI strains, such as the H7 strains that have been the cause of outbreaks in Australia. 

The traditional way that HPAI emerges in poultry requires 2 steps:

1. transmission of LPAI from wild birds to poultry (such as by close contact with droppings or nasal secretions), and
2. a chance mutation of the virus within poultry to convert it from LPAI to HPAI.

HPAI H5N1 does not require a mutation from LPAI, so any transmission from infected wild birds to poultry will result in HPAI.

This difference between H5N1 and other strains of HPAI is why we are not concerned about possible spread of the Australian H7 strains to New Zealand.

New Zealand, Australia, the Pacific Islands, and much of Antarctica remain free from HPAI H5N1

The likelihood of the introduction of HPAI H5N1 on pathways that we manage is low. As information emerges about the distribution of the H5N1 strain of the disease in Antarctica, we will have a better understanding about the likelihood of this strain reaching New Zealand through wild bird movements.

If HPAI H5N1 arrives in New Zealand, it could spread by direct contact between infected and healthy birds, or through contamination of equipment and materials, including water and feed.

Risk to human health and other animals from avian influenza

In other countries where HPAI H5N1 is present, human infection has been rare and generally only found in people who have had a lot of contact with infected birds or other infected animals.

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

Overseas, it has been found in a variety of land-based and marine mammals, which can be infected with the disease after contact with infected birds. In March 2024, HPAI H5N1 was detected in dairy cattle in the United States, with cattle generally recovering from the disease in 2 to 3 weeks with supportive care. US authorities have advised there is no risk to human health from consuming pasteurised milk and milk products, but have issued caution against consuming raw milk.

New Zealand does not import unpasteurised dairy products from the US.

Avian influenza, food safety, and human health

Dairy and other livestock that may be affected by avian influenza

Signs to look out for

The most obvious sign of HPAI is sudden death in several birds. Other signs in birds can include:

• weakness and trembling
• paralysis
• difficulty breathing
• lack of co-ordination
• blindness
• diarrhoea.

Poultry shows more severe signs than wild birds. These include lethargy, reduced appetite, droopy head, darkened or swollen comb/wattle, panting, and nasal secretions, unusual drop in egg production, and bleeding disorders.

Commercial poultry flocks and avian influenza

Domestic poultry and birds and avian influenza

Wildlife and avian influenza