New warnings have been given about the danger to humans posed by bird flu. The H5N1 virus has so far killed 166 people worldwide, but this figure could rise dramatically if the virus "mutates" say experts. "It could mutate into a big slime that eats everything in its way and kills everyone it touches," said Freddie Walker, a nine year old schoolboy from Tottenham. His friend, Ben Kelly, 10, had another theory. "I reckon it will mutate into a giant leopard which would rip off everyone's heads, and you couldn't even shoot it because it would be so strong, that would be wicked," he said. Last night Dr Jonathan van Tam of the Health Protection Agency, admitted that there was still considerable uncertainty among the scientific community as to how the virus will develop.