Why there's 'enormous concern' over the risk of bird flu spreading to humans
The World Health Organization has raised concerns about the spread of the H5N1 bird flu variant, which has an "extraordinarily high" mortality rate in humans.
Tomas Kauer - News Moderator 
The World Health Organization has raised concerns about the spread of the H5N1 bird flu variant, which has an "extraordinarily high" mortality rate in humans.
