FRIDAY, Nov. 20 (HealthDay News) -- Some areas of the United States are seeing declines in H1N1 swine flu activity, a federal health official said Friday, and while the disease remains widespread in 43 states, that's down from the 46 states reported last week.

"We are beginning to see some declines in influenza activity around the country, but there is still a lot of influenza everywhere," Dr. Anne Schuchat, director of the U.S. Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases, said during an afternoon press conference.

Current flu activity is higher than typically seen during the peak of seasonal flu season in mid-winter, Schuchat said, adding that she expects a lot more swine flu infections in the weeks and months to come.

The H1N1 virus continues to hit young adults and children hard. During the past week, 21 more children died from the flu, bringing to 171 the total number of confirmed deaths among children.

But, Schuchat cautioned, "This is just a partial counting. The estimates we provided last week provide a better estimate of the full toll that the virus has taken in the first six months of the pandemic."

Those estimates showed that at least 22 million Americans have come down with the swine flu since the virus first surfaced in April, and approximately 3,900 people have died, including an estimated 540 children.

Of the children who have died from swine flu, two-thirds had chronic health problems, such as asthma, cerebral palsy and muscular dystrophy, Schuchat said. The remaining one-third of the children were healthy and died of complications from bacterial infections, she said.

By way of comparison, seasonal flu -- which poses a greater health threat to older adults -- kills an estimated 36,000 Americans each year.

Meanwhile, the supply of H1N1 swine flu vaccine continues to grow, Schuchat said. As of Friday, 54.1 million doses had been produced by manufacturers -- an additional 11 million doses since last week, she said.

Earlier, the CDC predicted there would be 190 million doses available by year's end.

"We are in better shape today than we were a couple of weeks ago," Schuchat said. "I just want to say how sorry I am that people have been so frustrated, that people have had to wait in line, that people haven't always found vaccine at the end of the line."

Schuchat also said that, as of last Friday, a total of 94.5 million doses of seasonal (non-H1N1) flu vaccine were available. Manufacturers of the seasonal flu vaccine expect to produce a total of 114 million doses this flu season.

Also Friday, CDC officials confirmed that four patients infected with H1N1 swine flu who were treated at Duke University Hospital in Durham, N.C., over the past six weeks were found to be resistant to the antiviral drug Tamiflu. Tamiflu and a second antivral medication, Relenza, are considered key weapons against swine flu.

Health officials have been monitoring the H1N1 virus for signs that it might be mutating, making the antivral drugs ineffective.

But according to a Duke news release, the patients with Tamiflu-resistant swine flu were no sicker than patients who did not have drug-resistant illness. And all confirmed cases of Tamiflu-resistant virus have been susceptible to Relenza.

As a result, the CDC does not recommend any changes in the use of antiviral medications, the news release said.

On Thursday, a study presented at the American Society of Tropical Medicine and Hygiene annual meeting, in Washington, D.C., reported that people who were vaccinated for seasonal flu last year may have a 45 percent reduced risk of getting the swine flu. But, this protection seems to work for the oldest and youngest people, and not those in between, USA Today reported.

More information

To learn more about H1N1 swine flu, visit the U.S. Department of Health and Human Services.

SOURCES: Nov. 20, 2009, teleconference with Anne Schuchat, M.D., director, National Center for Immunization and Respiratory Diseases, U.S. Centers for Disease Control and Prevention; Nov. 20, 2009, news release, Duke University, Durham, N.C.

Copyright © 2009 ScoutNews, LLC. All rights reserved.