By Antony Clements-Thrower Beef sold in supermarkets is being tested for bird flu as the virus spread to cows for the first time. H5N1 was recently discovered in dozens of herds and two studies are looking to determine if particles were found in meat for sale in the areas where it was found in cows. Another will test the response to cooking meat infected with the virus. Bird flu first was first logged in 1996 and has killed millions of birds worldwide ever since. It has recently jumped to mammals including cats, foxes, penguins – and humans. The virus has not been found to spread between peopl…