Washington ? Federal health officials announced Monday that pandemic influenza-planning meetings will be held in all 50 states over the next four months to help bolster national preparedness for a possible outbreak of deadly avian flu.

Health and Human Services Secretary Michael Leavitt announced the plan at a national conference where health officials are fine-tuning community-response plans for the influenza threat.

Because local communities will bear the brunt of pandemic flu-response efforts, Leavitt urged all segments of the community to develop plans that address such issues as absenteeism, work stoppages and shortages of resources.

Avian flu currently is transmitted from animal to animal, mostly among birds. Humans can contract the disease after close contact with infected animals. To date, 133 people have contracted the virus and 68 have died, according to the World Health Organization.

Officials are preparing for a global pandemic that could be triggered if the virus, named H5N1, mutates into a form that can pass easily from human to human. No one would have immunity to this flu virus.

Leavitt said new government estimates showed that an influenza pandemic in Southeast Asia probably would reach the United States in 50 days. Within six weeks, some 722,000 U.S. residents would become ill.

By week nine, that number would grow to 37.4 million people and exceed 92 million people by week 16, Leavitt said. Federal estimates show that nearly half, 45 million, would seek medical care and roughly 209,000 would die in a “moderate” flu outbreak, similar to the 1957 virus that killed 70,000 people in the United States.

But 9.9 million could be hospitalized and more than 1.9 million would die if a “severe” pandemic strikes, similar to the 1918 outbreak that killed some 500,000 U.S. residents.