What is a zoonosis? Unfortunately, it's not a fun outing to Taronga, but instead any disease that infects or is carried by animals, which can also infect or be spread to people.
 
An estimated 60% of human infectious diseases around the world are zoonoses. And there's one that has the potential to do a lot of damage to chooks and humans: Bird flu, or Avian Influenza (AI), which has its reservoir in wild birds (they carry it without getting sick). AI comes in multiple varieties including Highly Pathogenic Avian Influenza, (HPAI). An example of HPAI is H5N1, which has lately smashed everything from parrots to penguins on every continent except Australia. 
 
Preparations for the worst are being made. What preparations can owners of backyard chooks make?
 
NSW has an excellent fact sheet here: https://www.health.nsw.gov.au/Infectious/factsheets/Pages/avian-influenza.aspx
 
...with the main take-aways being that bird flu is endemic in wild birds; that is, they carry it in their bodies all the time, and may not show any symptoms or get sick from it, but when they mix with domestic birds, such as your free-ranging leghorns, or contaminate your backyard by coming down to your birdbaths or chook feed dispensers, the virus can be passed to you, not to mention your budgie or your bantam.
 
What to do? Rehome your birds? If your household has immunocompromised people in it (eg young children, the elderly, anyone on chemo or other immunosuppressing medications) this is a valid step. Not just on account of AI, but other endemic zoonoses such as psittacosis, aka parrot fever, which has frequent outbreaks in the Blue Mountains due to our love affair with feeding native species. 
 
If you've ever worked at a big poultry producer, you'll know pet birds at home aren't allowed, because of biosecurity, ie the risk that your pet bird may be invisibly carrying something nasty. Poultry farmers have had the experience of driving vehicles through troughs of disinfectant, to keep contaminated soil out, and of performing a complete shower and change of clothes when passing in or out of the buildings.
 
This kind of barrier between your kitchen and backyard may not be practical. But you can try to approximate it by regularly washing hands with soap and water, wearing coveralls, and disinfecting your gumboots before and after attending to your chooks, even if you don't go the full PPE including P2 mask.
 
If you have a birdbath, situate it well away from areas that your chickens have access to. Fully emptying and disinfecting any food and water vessels every day is ideal. Always choose water containers that can be scrubbed and sterilised over a pond or waterfall which can never be cleaned and which will attract wild waterfowl.
 
Use netting, covered water and feed dispensers, and rat-proofed coops to reduce the chances of wild bird contact and/or contamination. 
 
Be careful around wild birds - enjoy watching them but don't encourage them to land on you, come into human-frequented spaces, or share your food.
 
Love your chooks and your aviary birds but don't kiss them!
 
Keep your annual human flu vaccination up to date. This reduces the chances a bird flu virus and a human flu virus can coexist in your body, potentially swapping genetic material with each other to mutate into the superflu that causes the next pandemic.
 
And if you notice a swathe of sudden deaths, coughing and sneezing, or other symptoms in your backyard flock, refer to this Bird Life Australia handout: https://birdlife.org.au/wp-content/uploads/2024/09/Avian-Influenza-Fact-Sheet-Sep-2024.pdf
 
...and AVOID, RECORD, & REPORT to the Animal Disease Hotline.