CHICAGO - Swine flu has killed nearly 10,000 Americans, including 1,100 children and 7,500 younger adults, and infected one in six people in the United States since arriving last April, health officials said on Thursday.

What we've seen for months is this is a flu that is much harder on younger people, Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, told a media briefing.

He estimated that between April and November 14 there had been nearly 50 million cases of H1N1 influenza in the United States, mostly in younger adults and children. That was more than double the CDC's estimate in November of 22 million Americans.

Frieden said more than 200,000 Americans had been hospitalized -- about the same number who are affected by seasonal flu in an entire year.

About 15 percent of the entire country has been infected with H1N1 influenza, or about one in six people, Frieden told a media briefing.

That still leaves most people not having been infected and still remaining susceptible to H1N1 influenza, he said.

He said supplies of H1N1 vaccine had continued to improve, and some 85 million doses of the vaccine had been made available for distribution so far, with 12 million more doses added this week.

That is up from 73 million doses a week ago -- but still far fewer than had been hoped for by this week.

Even so, Frieden said vaccine supplies had opened up enough that states were beginning to distribute the vaccine to the general population.

He urged people not to be complacent about getting the vaccine because of reports the current wave of H1N1 influenza is waning.

This is still a good window of opportunity to be vaccinated, he said. Vaccination remains the most important thing you can do to protect yourself and your family from H1N1 influenza.

He said the seasonal flu season was beginning and it was not clear what would happen with H1N1 or whether there would be a third wave of the virus in the spring.

We know that the more people who get vaccinated, the lower the likelihood will be of additional cases or a third wave, Frieden said.

In a typical year, seasonal influenza kills 36,000 Americans and puts 200,000 into the hospital.

(Editing by Peter Cooney)

Medicine