US influenza activity kept climbing last week, as several states outside the South reported widespread cases, and the 2009 H1N1 virus continued to be the predominant strain, according to the US Centers for Disease Control and Prevention (CDC).
Ten states reported geographically widespread flu activity, up from just four southern states the week before. The ten are Alabama, Alaska, Kansas, Louisiana, Massachusetts, New York, Pennsylvania, Texas, Virginia, and Wyoming.
Also, six states reported high influenza-like illness (ILI) activity as measured by visits to sentinel clinics, up from four states the previous week, the CDC reported. Nationally, 3.0% of medical visits were due to ILI, compared with the national baseline of 2.0%.
States with high ILI activity were Alabama, Louisiana, Mississippi, Missouri, Oklahoma, and Texas. Another eight states cited moderate ILI activity, and the rest had low or minimal numbers.
The CDC also reported a big jump in the percentage of respiratory samples that tested positive for flu: 24.1% (of 6,813 specimens), versus 17.8% a week earlier.
An H1N1 season so farOf the positive specimens, more than 98% were influenza A viruses, and 2009 H1N1—the former pandemic virus, now a seasonal strain—accounted for nearly all of those that were subtyped. Only 1.8% of the positive specimens were influenza B isolates.
Last week the...