The rising threat of bird flu

More species infected than ever, an uptick in human cases, and some concerning biological modifications. How close are we to a bird flu pandemic? We digest the last year of bird flu changes with virologist Tom Peacock and public health journalist Melody Schreiber. Also this week, we address the absurd problem of transporting something that can't be touched, we find out how animals make their epic migratory journeys, and Victoria Gill visits a town which has learnt to ward off a fearsome predator, polar bears.Presenter: Victoria Gill Producers: Ella Hubber & Gerry Holt Editor: Martin Smith Production Co-ordinator: Jana Bennett-Holesworth  & Josie HardyTo discover more fascinating science content, head to bbc.co.uk search for BBC Inside Science and follow the links to The Open University.