CDC: Influenza-like illness rates dips below national baseline

 ATLANTA — The Centers for Disease Control and Prevention on Friday reported that the national incidence of influenza-like illness dropped below the national baseline of 2.2% to 1.9% and is lower than reported during the previous week. "This fluctuation may be attributed in part to a reduced number of routine health visits during the Thanksgiving holidays, as has been observed in previous seasons," the agency speculated. 

Between Oct. 1 and Dec. 1, 417 laboratory-confirmed influenza-associated hospitalizations were reported (a rate of 1.5 per 100,000 population). Among all hospitalizations, 76.5% were associated with influenza A and 21.6% with influenza B. Among hospitalizations with influenza A subtype information, 96.6% were attributed to H3 and 3.4% to 2009 H1N1. 

The most commonly reported underlying medical conditions among hospitalized adults were metabolic conditions, cardiovascular disease, obesity and chronic lung disease (excluding asthma). Among 11 hospitalized women of childbearing age (15-44 years), one was pregnant. The most commonly reported underlying medical conditions in hospitalized children were asthma, cardiovascular disease, neurologic disorders and obesity. More than 40% of hospitalized children had no identified underlying medical conditions. Additional FluSurv-NET data can be found here. 

For the week ended Dec. 1, Alabama, Louisiana, Mississippi and Texas all reported high levels of ILI activity. Georgia, Missouri and Tennessee reported moderate levels of ILI activity. 

However, according to geographic spread of influenza (which does not account for the severity of influenza activity) CDC reported widespread activity in eight states: Alabama, Alaska, Mississippi, New York, North Carolina, Ohio, Rhode Island and South Carolina. 

When national ILI rates eclipsed 2.2% last week, it marked the earliest in the season that had happened for many years, excepting the year H1N1 was prevalent. The 2007/2008 flu season was the last moderately severe season, and that season didn't cross the 2.2% threshold until late December 2007/early January 2008. 

As part of CDC's FluView this season, the agency is releasing enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. To access these tools visit http://www.cdc.gov/flu/weekly/fluviewinteractive.htm.