Many humans may already have some immunity to H5N1 bird flu, raising hopes that the virus could pose less of a threat than previously thought, new research suggests.

A first-of-its-kind trial has been launched to test a new vaccine for bird flu in humans, amid the "real possibility" of human-to-human transmission. Thousands of people in the UK are expected to be recruited for the study, with poultry farmers or those ...

The findings show how the H5N1 bird flu virus is evolving in livestock and what that may mean for human health.