Across the world a highly pathogenic strain of avian influenza known as H5N1 has been causing widespread concern. This strain has affected birds, marine mammals, land mammals and a small number of humans. Australia remains free of this virus, but the global situation is changing quickly and it is important for the wildlife community to understand what is happening and what to look out for.

Where This Strain Came From

The current H5N1 strain did not appear suddenly. It has a long evolutionary history that began in 1996 when an early form of H5N1 was detected in domestic geese in Guangdong, China. Over the following decades the virus spread through poultry systems across Asia, Europe and Africa. Around 2014 it evolved into a new genetic group known as clade 2.3.4.4. This group produced several variants that spread more easily in wild birds.

In 2020 and 2021 a particular branch of this clade emerged in Europe. This is the variant now circulating globally. It spread rapidly because infected wild birds were able to migrate long distances while carrying the virus. By 2022 it had reached North America, South America, Africa and parts of Asia. By 2023 it had reached Antarctica. Australia is now the only continent where this strain has not been detected.

Why It Has Spread So Widely

Several factors have contributed to the global spread. Migratory birds have carried the virus across continents. Poultry production systems have provided opportunities for the virus to mutate and recombine. High densities of wild birds in coastal and wetland areas have allowed the virus to circulate easily. Once the virus reached new regions it encountered species that had no previous exposure and therefore no immunity.

Impacts on Birds

The virus has caused severe disease in many bird species. Infected birds may show neurological signs such as tremors, loss of balance, head tilting or circling. They may also show respiratory signs including gasping or nasal discharge. Some birds die suddenly with no visible symptoms. Seabirds such as terns, gulls and pelicans have been heavily affected in other parts of the world.

Impacts on Marine Mammals

One of the most concerning developments has been the spread of H5N1 into marine mammals. In South America more than 30,000 sea lions have died. Southern elephant seal colonies have experienced catastrophic losses with some rookeries losing more than 90% of pups in a single season. Affected animals often show severe neurological symptoms including seizures, disorientation, paralysis & difficulty breathing.

These events appear to be driven by infected seabirds shedding the virus into the environment. Marine mammals become infected when they eat sick birds, scavenge carcasses or inhale contaminated droplets at crowded haul outs. Evidence from South America suggests that seal to seal transmission has occurred which is a significant development in the behaviour of this virus.

Impacts on Land Mammals

Land mammals such as foxes, bears, cats & cattle have also been infected overseas. These infections usually occur when animals scavenge infected birds. Symptoms often include seizures, confusion, circling, tremors and sudden death. In cattle the symptoms have been milder and include reduced milk production, fever & eye inflammation.

Human Infections

Human infections remain rare and almost always involve direct contact with infected animals. Symptoms can include fever, cough, sore throat, fatigue, headache and in some cases eye inflammation. There is no evidence of sustained human to human transmission. The overall risk to the public remains low, but health authorities continue to monitor the situation closely.

Why Australia Is Still Free of This Strain

Australia has strong biosecurity systems and benefits from geographic isolation. These factors have helped keep the virus out so far. However experts note that luck has also played a role. Migratory birds connect Australia to regions where H5N1 is circulating, and these pathways remain the most likely route for the virus to enter the country.

How the Virus Could Reach Australia

The most likely carriers are migratory shorebirds that travel between Asia & Australia each year. Species such as godwits, knots, sandpipers, curlews, terns & some gulls follow flyways that pass through regions where the virus is present. These birds arrive in northern Australia during the spring migration season. If the virus enters Australia it is expected to appear first in coastal or wetland birds.

Marine mammals cannot bring the virus to Australia. They are victims rather than vectors. The virus would need to arrive in birds first before it could affect seals or sea lions in Australian waters.

What It Would Mean for Australian Wildlife

If H5N1 reaches Australia the impacts on wildlife could be severe. Native birds including parrots, waterbirds & seabirds may experience high mortality. Endangered species such as the Australian sea lion could be at significant risk. Waterbirds and coastal birds in WA would likely be among the first affected due to the large numbers of migratory species that visit the region.

Symptoms to Watch for in Birds

Wildlife carers and community members should be aware of the following signs:

• loss of balance or inability to stand
• tremors or seizures
• walking in circles
• difficulty flying or sudden collapse
• respiratory distress such as gasping
• unusual tameness or isolation from the flock
• clusters of sick or dead birds

Symptoms to Watch for in Marine Mammals

Although marine mammals cannot bring the virus to Australia, they may be affected if the virus arrives. Symptoms include:

• seizures
• disorientation
• paralysis
• laboured breathing
• foaming at the mouth
• large numbers of animals affected at once

What To Do If You Encounter a Suspected Case

If a bird or marine mammal appears to be showing unusual neurological signs or if there are multiple sick or dead animals in one area, it is important to keep a safe distance. Do not touch or move the animal. Note the location, species and symptoms. In WA suspected cases should be reported to the Emergency Animal Disease Hotline on 1800 675 888. This number connects to the Department of Primary Industries & Regional Development which coordinates responses to potential avian influenza detections.

Personal Protection When Handling Birds

Most wildlife handling in Australia does not involve avian influenza, but good personal protection is always important. When handling any sick or dead bird it is recommended to use nitrile gloves, eye protection, a P2 or N95 mask, long sleeves and closed shoes. Avoid disturbing feathers and keep the bird's head pointed away from your face. After handling wash hands thoroughly and disinfect equipment. If avian influenza is suspected do not handle the bird unless instructed by authorities.

Where To Get Reliable Updates

If H5N1 is ever detected in Australia the first official notifications will come from the Department of Agriculture, Fisheries and Forestry at the national level and from state biosecurity agencies such as DPIRD in WA. Wildlife Health Australia will provide updates on detections in wild birds and marine mammals. ABC News is a reliable source for public information. Local councils may also issue warnings or temporary closures of affected areas.

Why This Information Matters

Australia has a unique and vulnerable wildlife community. Understanding the global situation helps wildlife carers, volunteers and the public stay informed and prepared. Early reporting of unusual wildlife deaths is one of the most important tools for protecting native species. While the current H5N1 strain has not reached Australia, awareness and good practice can help ensure that any potential incursion is detected quickly.