US flu activity remains low, CDC says

Dec 30, 2011 (CIDRAP News) – Influenza activity in the United States remains low, with all major indicators below baseline, the Centers for Disease Control and Prevention (CDC) reported today.

In its weekly FluView update, the agency said that, during the week ending Dec 24, of 2,652 specimens tested and reported to the CDC, 97 (3.7%) were positive for flu, which was up from 2.1% the week before. CDC region 8, which comprises Rocky Mountain states and the Dakotas, had the highest percentage, 7.9%.

The proportion of visits for influenza-like illness (ILI) nationwide was 1.5%, up slightly from 1.4% the week before but still well below the national baseline of 2.4%.

Similar to the previous week, one state (Georgia) reported moderate ILI activity, one state (Minnesota) and New York City reported low ILI activity, and 47 states experienced minimal activity.

Measures of geographic spread also changed little week over week. Colorado experienced regional spread, Alabama and Virginia local spread, 37 states and Guam sporadic activity, and the rest of the country no flu activity.

Of the 90 flu viruses that labs antigenically characterized, 70 (78%) were H3N2, 9 (10%) pandemic 2009 H1N1, and 11 (12%) influenza B. Of the 11 influenza B viruses, 7 were of the Victoria lineage and 4 were of the Yamagata lineage.

"It is too early in the influenza season to determine how well the seasonal influenza vaccine strains and circulating strains will match," the CDC said.

No pediatric flu deaths were reported this week, and no resistance to common antiviral drugs was detected.

Meanwhile, the European Centre for Disease Prevention and Control (ECDC) said in a report today, "With little evidence of sustained transmission in EU/EEA countries at week 51, the annual influenza seasonal epidemic in Europe is yet to start."

The ECDC reported that, of 539 specimens collected, 35 (6.5%) tested positive for flu. The agency said, "Although this is still a low percentage, it has increased over the last 4 weeks." The ECDC noted that 248 (91.5%) of 271 subtyped influenza A viruses were H3 strains.

See also:

Dec 30 CDC update

Dec 30 ECDC report

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