Pandemic Influenza

Influenza is a contagious infection of the nose, throat, and lungs caused by influenza viruses. There are two main virus types: A and B. Each type includes different strains that change from year to year. An influenza pandemic is a global outbreak of a new influenza A virus — when a non-human (novel) influenza virus changes in such a way that it is able to infect humans easily and spread easily from person to person.