How can we diagnose swine flu and what is the accuracy of the diagnosis?

By lab tests. "swine flu" is one of a series of strains of influenza viruses, some of which seem to prefer or be transmitted through an animal host to humans. The symptoms do not differ much from other strains of influenza, and the diagnosis is made by isolation of the virus and testing for its genetic composition, the two major antigens being neuraminidases and hemagglutinins (if that makes any sense to you).