Kung fu king Jackie Chan is starring in a new short - he appears in a United Nations Children's Fund (Unicef) public service announcement warning children about the dangers of bird flu. The goodwill ambassador shot the advertisement at an international school in Hong Kong, according to a statement on the star's website. Bird flu has caused the deaths of 115 people since 2003 with experts fear a future pandemic, should the virus mutate and become contagious in humans.