How worried should we be about avian flu?

Avian flu has devastated poultry farms and wild bird populations around the world and now it's spread to mammals such as mink and seals. Cases in humans have been rare but worryingly fatal in more than half of the recorded incidences. How worried should we be about the risk of a new global pandemic?Joining David Aaronovitch in The Briefing Room are: Wendy Barclay, Head of the Department of Infectious Disease and Chair in Influenza Virology at Imperial College London Dr Wendy Puryear, Molecular virologist, Tufts University Prof Ian Brown, Head of Virology at the Animal and Plant Health Agency Marion Koopmans, Head of the Department of Virology at the Erasmus Medical Centre in RotterdamProducers: Kirsteen Knight, Cecilia Armstrong and Ben Carter Production Coordinators: Siobhan Reed and Maria Ogundele Sound mix: Rod Farquhar Editor: Richard Vadon