More action must be taken to prepare for a "devastating" global flu pandemic, the head of the US government's health watchdog has warned.

Julie Gerberding, director of the Atlanta-based Centres for Disease Control and Prevention (CDC), said the world's defences against flu were improving but remained inadequate. Fears of apandemic have been heightened by the spread of avian influenza, or bird flu, across Asia towards the borders of Europe, with at least 57 people killed by a variety of the H5N1 bird flu strain.