That's because, since August, 12 people have come down with a specific sub-type of the disease.
It's known as the H3N2 virus. So far it has turned up in Indiana, Iowa, Maine, Pennsylvania and West Virginia.
Eleven of those infected were children. Three patients were hospitalized. But all have fully recovered.
The swine flu became a global pandemic beginning in 2009. An estimated 43 to 89 million caught swine flu, and up to 18,000 died from it, according to the CDC.
The World Health Organization officially declared an end to the pandemic last year.
This year's flu vaccine is good against the H3N2 variant.
The CDC recommends that everyone six months and older get a flu shot.
