Virologists warned on Tuesday that there was no vaccine against a mutant strain of H5N1 bird flu now spreading in China and Vietnam and called for closer monitoring of the disease in poultry and wild birds to stop it spreading to people. The call came after the U.N. Food and Agriculture Organization (FAO) warned on Monday of a possible resurgence of bird flu and said a mutant strain of the H5N1 was spreading in Asia and beyond. While scientists are uncertain if this new strain -- called H5N1-2.3.2.1 -- is more virulent in people, they said it was different enough from its predecessor to escape a human H5N1 vaccine that can tackle the parent strain.
