This year’s flu season is shaping up to be “worse than average and particularly bad for the elderly,” Dr. Thomas R. Frieden, the nation’s top federal disease-control official, said Friday.

But the season appears to have peaked, added Dr. Frieden, the director of the Centers for Disease Control and Prevention, with new cases declining over most of the nation except for the far West.

Spot shortages of flu vaccine and flu-fighting medicine are occurring, but that reflects uneven distribution, not a supply crisis, federal officials said. They urged people seeking flu shots to consult flu.gov and doctors to check preventinfluenza.org for suppliers.