The evidence was a standard immunological test: Antibodies that cling to and inactivate swine flu viruses also clung to and inactivated this new virus. The test was to grow the virus in a fertilized hen’s egg and then remove the cloudy fluid that was brimming with virus. Mix the virus with red blood cells. If they clump, you have a flu virus. Then mix the virus with antibodies to particular strains of flu and try the red blood cell test again. When you hit on the right flu strain, the virus will be inactivated by the antibodies and the red cells will no longer clump.
