26/06/2026
Bird flu is a hot topic currently so here’s some info you may find interesting.
There are multiple subtypes of influenza A viruses, defined by combinations of haemagglutinin (H) and neuraminidase ( N ) surface proteins. The attached image shows the 18 known haemagglutinin subtypes (H1–H18) and the range of animal species they can infect. H1 and H3 are the subtypes the most common human influenza viruses. However, other subtypes are also capable of infecting humans, including H5, H6, H7, H9 and H10. The current strain of concern is highly pathogenic avian influenza H5N1, clade 2.3.4.4b (a clade refers to a genetically related group of viruses that share a common evolutionary lineage). This particular clade has spread globally in recent years with extensive circulation in wild bird populations, spillover into a range of mammalian species, and ongoing genetic evolution through mutation and reassortment.
Until recently, preparedness in Australia largely focused on expected introduction via the East Asian–Australasian Flyway, a major migratory pathway for birds moving between Asia and Australia. However, detections in this past week suggest the virus has been introduced via southern oceanic routes, following significant mass casualty events of penguins and seals on Heard Island earlier this year. Current detections in Australia have been in migratory, ocean-dwelling birds (Brown Skua and Giant Petrals) however there is concern it will eventually spread into native bird populations that move between coastal and inland environments, increasing geographic distribution.
Overseas, H5N1 has also spread extensively through dairy cattle in the United States, with the virus detected in milk from infected cows. Fortunately, standard pasteurisation is highly effective at inactivating the virus, and there is currently no evidence that people have become infected from drinking pasteurised milk. While infection through consuming raw/unpasteurised milk appears to be unlikely, widespread exposure of mammals to the virus provides additional opportunities for viral evolution and adaptation. This is why surveillance in livestock, rapid detection of new cases, and avoiding consumption of raw (unpasteurised) milk remain important public health measures.
Surveillance for avian influenza relies on a combination of wildlife monitoring and laboratory testing including targeted sampling of wild birds, poultry, and high-risk environments. Laboratory testing uses RT-PCR (polymerase chain reaction) to detect viral genetic material and confirm subtype as well as whole genome sequencing to determine clade, track transmission pathways, and monitor mutation, as well as antigenic and virological analyses to assess changes in transmissibility. These typically involve cloacal and oropharyngeal swabs, and sometimes tissue samples from deceased animals. Environmental sampling, such as wastewater or habitat sampling, can also be used in broader influenza surveillance programs.
One important difference between avian and human influenza is the part of the body the virus prefers to infect. Influenza viruses replicate best at particular temperatures. In humans, our core body temperature is generally too warm, so influenza primarily infects the cooler tissues of the upper and lower respiratory tract, causing a respiratory illness. Birds have a higher body temperature, and avian influenza viruses predominantly replicate in their intestinal tract, making it largely a gastrointestinal disease in birds. As a result, infected birds shed large amounts of virus in their faeces, meaning contaminated bird droppings and the environments they contaminate are a major route of transmission between birds, even after the bird has moved on.
Human infections are rare at this stage are associated with close contact with infected animals, particularly poultry or livestock, and there has been no confirmed human to human transmission. People working with birds or livestock are advised to follow established infection prevention measures, including appropriate personal protective equipment (PPE), hygiene practices, and prompt reporting of unusual illness or deaths in animals.
Seasonal influenza vaccination remains important, as while it is not expected to provide significant protection against H5N1, it is expected to provide some cross-protection against related influenza strains and, importantly, reduces the risk of simultaneous infection with seasonal influenza and avian influenza viruses (co-infection increases the theoretical risk of viral reassortment). The seasonal influenza vaccine is currently available for free until the end of next month. Children under 12 years can also access the needle-free FluMist vaccine, while young people aged 12–18 years can receive the standard injectable vaccine at no cost or pay for the FluMist privately.
Pet owners should also be cautious. While infections in dogs are possible, cats are particularly susceptible to H5N1 and should be contained to your property. Avoid allowing pets to interact with sick or dead birds or consume raw meat or raw (unpasteurised) milk, and seek veterinary advice if they become unwell following potential exposure.
Continued surveillance, early reporting of unusual wildlife deaths, and adherence to biosecurity measures remain the most important tools for limiting spread and protecting both animal and human health.
