Meanwhile, the supply of H1N1 vaccine continues to grow, Frieden said. There are now 85 million doses of vaccine available, up another 12 million doses from last week.
"This is a good window of opportunity to get vaccinated," he said. "We don't know what the future will hold in terms of H1N1 influenza."
The swine flu continues to produce mild infections in most people, with recovery taking about a week. But certain groups remain at risk for complications, including pregnant women, children and young adults, and people with chronic health problems, such as asthma, diabetes and heart disease.
Frieden also noted that cases of the regular, seasonal flu have begun to show up. Influenza B has already killed one child, he said.
So far this year, about as many people as last year have gotten a seasonal flu shot. With 109 million doses of seasonal flu vaccine available, most of the supply has been shipped. But, people are still experiencing shortages of this vaccine, Frieden said.
In related news, health officials in Vietnam said they have identified a cluster of swine flu cases resistant to the antiviral drug Tamiflu. The cases involved seven people who had traveled together on a long train ride in July. They did not know each other before the trip, and all recovered, according to a report in the Dec. 10 issue of the New England Journal of Medicine.
An estimated 100 cases of Tamiflu-resistant H1N1 flu have been reported worldwide.
For more on H1N1 swine flu, visit the U.S. Health and Human Service Administration.
SOURCES: Dec. 10, 2009, teleconference with Thomas R. Frieden, M.D., M.P.H., director, U.S. Centers for Disease Control and Prevention; Dec. 11, 2009, Morbidity and Mortality Weekly Report, U.
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