Health officials say swine flu infections continue to wane, with only half the states reporting widespread cases.

In late October, 48 states were reporting widespread swine flu. But since then, there's been a decline across the country.

The figures reported Friday by the Centers for Disease Control and Prevention are for the week of Thanksgiving.

Since it was first identified in April, swine flu has sickened an estimated 22 million Americans and killed 4,000. It has proved to be similar to seasonal flu but a bigger threat to children and young adults.