By Kate Kelland, Health and Science Correspondent LONDON (Reuters) - Scientists are to create mutant forms of the H7N9 bird flu virus that has emerged in China so they can gauge the risk of it becoming a lethal human pandemic. The genetic modification work will to result in highly transmissible and deadly forms of H7N9 being made in several high security laboratories around the world, but it is vital to prepare for the threat, the scientists say. ...{br}{br}View the Entire Article{br}