Bird flu (or avian influenza) refers to strains of flu viruses that mainly affect birds. The current strain of concern is known as H5N1.

Since 2020, a sub-strain of H5N1, known as 2.3.4.4b, has been circulating around the world. This has resulted in the deaths of millions of birds, including poultry. It has also crossed into other species, including dairy cows in the United States, and marine mammals.

In June, the first cases of H5N1 influenza were reported in Australia, first in migratory birds, then in local wild birds.