Avian influenza virus (AIV) infection can cause significant infectious disease in poultry and can also infect and cause disease in a range of other species including wild birds and humans. There are two categories of AIVs: low pathogenicity and high pathogenicity.
Wild waterfowl and to a lesser extent, shorebirds are the main natural reservoirs for low pathogenicity strains of AIV, with infection typically resulting in only mild or no clinical signs of disease in these birds. Whilst a rare occurrence, low pathogenicity strains of AIV can spill over from wild bird populations into poultry where they can then mutate into high pathogenicity viruses leading to severe disease and high mortality.
The National Avian Influenza Wild Bird Surveillance (NAIWB) program collects and screens samples from Australian wild birds for AIVs and the data generated are used to monitor and understand avian influenza in wild birds in Australia. Over the life of the 18-year program, thousands of Australian wild bird samples have been screened with no high pathogenicity AIVs detected in our wild birds.
Since 23 December 2021 more than 1050 new high pathogenicity AIV outbreaks were reported in domestic and wild birds across 4 geographic regions: Europe, Asia, Africa, and North America. The high pathogenicity virus strains (goose/Guandong HPAI H5Nx virus clade 2.3.4.4) that are currently being detected in the northern hemisphere emerged around 2010 and have limited health impacts in some wild bird species, enabling spread of the virus by these species more widely than if they became ill. Further, clade 2.3.4.4 B viruses (a subclade of the 2.3.4.4 viruses) can infect a large range of bird species. While clade 2.3.4.4 B has been detected in apparently healthy wild birds, it has also contributed to a number of substantial wild bird mortality events.
Sequence analysis of AIVs detected in wild birds through the NAIWB program contributes to tracking Australian virus evolution and dynamics, maintaining currency of diagnostic tests, and maintaining a virus sequence library allowing comparison of Australian and overseas strains. To date, Australia remains free from these strains of viruses currently being detected in the northern hemisphere.
Studies to date have found no evidence that migratory birds are carrying infectious high pathogenicity viruses when they arrive in Australia. Analysis of the most recent outbreaks of AIV in poultry in Victoria were found to be strains closely related to those circulating in Australian wild birds, and not imported avian influenza virus strains from Asia or elsewhere. However, the current widespread and frequent detection of high pathogenicity AIVs in the northern hemisphere likely means an increased level of risk to Australia, although previous research has assessed the overall risk of introduction of high pathogenicity AIVs to Australia to be low*.
Increased awareness and vigilance by Australian poultry producers and wildlife health professionals is advised. There is a need to remain vigilant by:
Further technical information:
*Note: a formal risk assessment for the current HPAI strains circulating has yet to be undertaken.