A new genetic technique developed by US and Japanese scientists could help drugs firms produce a vaccine for the deadly strain of bird flu more quickly, researchers said in a specialized magazine. The improved “reverse genetics” technique makes the disarmed viruses that are the seed stock for producing large quantities of flu vaccine, said the study’s co-author, Yoshihiro Kawaoka of the University of Wisconsin.It could assist in the rapid manufacture of a vaccine for the virulent H5N1 strain of avian flu, which has killed more than 60 people in Asia since late 2003.The new method, stemming from a technique Kawaoka developed in 1999, makes it easier to produce a seed virus in monkey kidney cells, which, like tiny factories, churn out millions of copies of the disarmed virus for vaccines.The genetically altered virus is then seeded into chicken eggs to generate the vaccine used in inoculations, the researchers said in this week’s issue of the Proceedings of the National Academy of Science.