Margaret Chan, the agency's director general, said the organization's Emergency Committee, in a meeting held by teleconference, concluded the world is now moving to the post-pandemic period. She said the committee considered reports from around the globe and from countries where influenza is currently infecting people.
Epidemiologists expect the H1N1 strain to behave like the seasonal flu, she said, with yearly outbreaks over the next few years.
Chan said the current patterns of H1N1 infection have changed from those seen during the height of the pandemic. For one thing, outbreaks out of season are no longer being reported.
While seasonal influenza, which kills hundreds of thousands of people yearly, tends to strike hardest at the very young and the elderly, H1N1 fatalities, which totaled roughly 15,000, often tended to occur among healthy teenagers and young adults, resembling the influenza in the pandemic after World War I that killed tens of millions of people. Chan said H1N1 is likely to continue to cause serious illness among the young.