Health experts have warned flu H1N1 is spreading and must be watched carefully in case it mutates.Close to 100 percent of the globe has been affected by the deadly bug, with some 800 deaths. In England alone, the number of new cases nearly doubled last week to an estimated 100,000. In Europe, it is feared the infection rate could rise dramatically once winter arrives. The World Heath Organisation is looking into ways of speeding up the production of vaccines before the autumn and full flu season begins. Earlier, it said it expects makers to have shots for the virus, ready for use in just over a month. However, it stressed safety over any new vaccine would not be compromised. Last week, officials said the current H1N1 virus, which has commonly been referred to as Swine flu, was the fastest moving pandemic ever recorded.