Although influenza activity is sporadic throughout the United States, there are signs that it is increasing, particularly in the Southeast, according to health officials.
The sharpest increases have occurred in Georgia, which is experiencing regional disease activity with particular impact on school-age children, Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases and assistant surgeon general of the U.S. Public Health Service, told reporters on a conference call.
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More than 20 percent of specimens tested in that state are positive for influenza -- mostly the B strain -- compared with 10.7 percent nationally. When that number exceeds 12 percent, Schuchat said, the flu season has arrived.
"If you've been thinking about getting vaccinated for influenza, now is a very good time to do so," said Dr. Howard Koh, assistant secretary for health for the Department of Health and Human Services.
The conference call kicked off this year's National Influenza Vaccination Week, which starts on Dec. 5. The effort is aimed at highlighting the importance of and increasing the use of flu vaccine before the traditional winter peak in disease activity. The 2010-2011 season marks the implementation of a universal recommendation for everyone older than 6 months to receive the vaccine.
Schuchat said there was no way of predicting how severe the season would be, and both she and Koh stressed the unpredictability of influenza viruses, pointing to last year's pandemic estimated to have killed more than 12,000 people. They cautioned against complacency based on the quiet start to the flu season thus far.
Because of the uncertainty, everyone should be vaccinated, the officials said.
This season's trivalent vaccine protects against the A/H3N2, B, and 2009 H1N1 pandemic strains.
Of the specimens tested nationally so far, most contain the A/H3N2 and B strains, with a minority containing the pandemic strain. The vaccine appears to be well matched to the circulating strains, according to Schuchat.
Preliminary CDC surveys indicate that about one-third of adults and children have been vaccinated, a coverage rate equal to or slightly ahead of last year at this time, Schuchat said.
She encouraged people to get vaccinated before the flu season gets fully under way and noted that about 160 million doses have already been distributed in the U.S., more than has been available in previous seasons.