Washington ? Influenza is circulating unusually early this year with cases in all 50 states — nearly all the swine flu variety, government health officials said Friday.

The highest concentration of flu cases is in the Southeast and a few other states, Dr. Anne Schuchat of the Centers for Disease Control and Prevention said at a briefing.

The good news is that testing of vaccines for swine flu show that they work with a single dose and take effect rapidly.

Supplies of swine flu vaccine are expected to be available in mid-October, but the seasonal flu vaccine is available now and officials have encouraged people to get it.