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CDC: Influenza activity on a downward trend, but significantly higher than last year


ATLANTA Influenza activity is falling, but it’s still pretty significant, Thomas Friedman, director of the Centers for Disease Control and Prevention, reported during a press briefing Tuesday afternoon. For the week ended Nov. 21, 32 states reported widespread activity, representing the fourth consecutive week of decline in flu activity. However, compared with last year when flu activity was relatively nonexistent, flu activity still is significantly high.

“We’re not out of the woods, yet,” he said. However, the drop off in activity coupled with a growing vaccine supply may make for a good opportunity to inoculate more people should H1N1 activity become resurgent. “We continue not to have as much vaccine as we’d like to at this point,” Friedman said, but H1N1 vaccine availability is on the rise.

Friedman noted that there is quite a bit of debate around whether or not activity of the novel H1N1 influenza will increase again in December/January, or even later in the season. During the course of the 1957/1958 pandemic, influenza rates spiked earlier in the season, dropped in activity, and then spiked again in December. “But if you’ve seen one flu pandemic, you’ve seen one flu pandemic,” Friedman cautioned, noting that with all of the variables surrounding influenza, it’s difficult to draw correlations between one pandemic and the next.

According to Friedman, many of the world’s leading influenza experts are split as to whether or not H1N1 will resurge. Friedman  noted that there have been reports coming out of Norway of a mutated H1N1 virus that’s more virulent than the current strain.

Seasonal flu is also beginning its course. To date, CDC has antigenically characterized one seasonal influenza A (H1N1), three influenza A (H3N2), four influenza B, and 412 2009 influenza A (H1N1) viruses collected since Sept. 1. The one  seasonal influenza A (H1N1) virus is related to the influenza A (H1N1) component of the 2009-10 Northern Hemisphere influenza vaccine (A/Brisbane/59/2007).

Influenza B viruses currently circulating globally can be divided into two distinct lineages represented by the B/Yamagata/16/88 and B/Victoria/02/87 viruses. The influenza B component of the 2009-10 vaccine belongs to the B/Victoria lineage. The four influenza B viruses tested belong to the B/Victoria lineage and are related to the influenza vaccine component for the 2009-10 Northern Hemisphere influenza vaccine (B/Brisbane/60/2008).

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