Understanding and controlling pandemic influenza.

Influenza A virus infection is a zoonosis. The natural reservoirs of the viruses are migratory water birds, particularly ducks. Through a process of reassortment of the genomes of avian and human influenza viruses, novel virus strains may arise to which humans are not immune. Such a virus can spread rapidly throughout populations as a pandemic, usually with serious consequences. Effective preparedness for future influenza pandemics depends on robust global surveillance of avian, swine, mammalian, and human influenza and continuous updating of our Library of Influenza Viruses from these hosts to aid diagnosis and vaccine production. Enhancing and refining strategies for controlling seasonal influenza, including the development of more potent vaccines and therapeutic medicines, that can be seamlessly implemented when a new influenza virus emerges is crucial. This review, which draws on more than half a century of our research on the ecology of influenza viruses, describes how pandemic influenza viruses arise and outlines strategies for preparedness against future pandemics.