Seven states -- California, Nevada, Arizona, New Mexico, Utah, Colorado, and Texas -- now show what scientists classify as widespread flu activity. The number is up from four states two weeks ago, according to data released by the CDC.
In all, the agency has received 63,104 reports of persons contracting flu-like illness as of Dec. 31, placing the 2005-2006 flu season at about average for yearly U.S. flu activity.
"Basically, activity is increasing as you'd expect for this time of year. This [season] is lighter than some, but activity is staring to pick up," says Lynnette Brammer, an epidemiologist who oversees domestic flu surveillance for the CDC.
The yearly march of influenza across the nation is notoriously unpredictable, experts warn. This year's flu season comes as authorities continue efforts to speed distribution of millions of flu vaccine doses that in some cases fell victim to production delays.
The delays caused some shortages mostly at smaller health clinics, while large vaccine purchasers like drug store and grocery chains moved to the front of the line for supplies.
The season also comes as epidemiologists remain on the lookout for any signs that H5N1, the virus that causes bird flu, has infected a human in the U.S. So far officials have seen "none at all," Brammer says.
The government has recorded five fatal flu cases in children this season. Reports from 122 cities show seven influenza deaths in adults, though Brammer warned that the CDC expects many more. Influenza kills an average of about 36,000 Americans each year.
The agency reported that more than 90% of samples collected from infected persons showed the presence of the H3 subtype of influenza A, a relatively common strain that can cause more severe illnesses and a higher-than-normal rate of hospitalizations and fatalities.
"Those are years when you see increases in deaths. H3 years tend to be more severe years. But right now there's not much out of the ordinary," Brammer says.
SOURCES: Weekly influenza surveillance report, week ending Dec. 31, 2005, CDC. Lynette Brammer, epidemiologist, influenza branch, CDC.
By Todd Zwillich
Reviewed by Louise Chang, MD
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