Birds & Bird Flu graphics showing avian influenza (H5N1) mixing with other 'flu strains; image of bird flu viruses and human flu viruses entering the same cell and pandemic influenza emerging, diagram of replication of viruses showing reassortment of viral RNA genome segments (genetic mixing or recombination) creating a new viral strain (reassortant) with the potential to create a catastrophic new flu pandemic against which no flu vaccine will protect.