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A 'window of opportunity' for preventing another wave of swine flu

December 1, 2009 | 11:15 am

PigWith activity of the pandemic H1N1 influenza virus declining across the country and the availability of the vaccine against it growing, health authorities have "a window of opportunity" for preventing or minimizing another wave of infections in the coming months, said Dr. Thomas R. Frieden, director of the Centers for Disease Control and Prevention, at a news conference this morning.

In planning for the short-term future, CDC officials conducted an informal poll of about a dozen internationally recognized flu experts, asking them if they thought there would be another wave of infection this winter. "About half said yes, half said no, and one said 'Flip a coin,' " Frieden said. "We don't know what the future will hold."

Figures released Monday showed that influenza activity had declined for the fourth consecutive week, with only 32 states now reporting widespread activity, down from 48 states a month ago. "Flu is going down, but it is far from gone," Frieden said. "The flu season lasts until May. Only time will tell what the flu season will bring."

Frieden said nearly 70 million doses of swine flu vaccine are now available, an increase of 9 million since Wednesday. "We are seeing that more people are getting vaccinated and protected and, as that happens, it becomes harder for the virus to spread," he said. But he also cautioned that, as more people become immune, that puts increasing pressure on the virus to mutate to a new form.

Frieden spoke briefly about the mutated strains of the virus that have been detected in some patients recently in Norway and China. There has been speculation that the mutant form may be somewhat more virulent because it is able to penetrate farther into the lungs. But Frieden noted that the virus has been  observed sporadically during the pandemic and many scientists believe that it is a mutation that evolves in an infected patient, allowing the virus to burrow farther into the lungs. He noted that physicians have seen patients with the mutant strain deep in the lungs and a different strain higher up, suggesting that the mutant strain was created in situ. In any case, he added, there is no evidence that the mutant strain is spreading and "it is not likely to become the dominant strain."

-- Thomas H. Maugh II