Generally speaking, "bird flu" refers to avian influenza, a virus that mainly infects birds but can also infect people and other animals. Although H5N1 is the most well-known variant that has caused worry recently, other strains, like H7N9 and H5N8, have also been watched for their ability to infect people.
Concerns over different strains of avian influenza were still present as of my latest knowledge update in October 2023 because of their propensity to evolve, trigger epidemics in poultry, and, in rare instances, spread to people. Human symptoms can vary from minor flu-like symptoms to serious respiratory illnesses, with severe cases often having a high death rate.