Key Flu Indicators

Each week CDC analyzes information about influenza disease activity in the United States and publishes findings of key flu indicators in a report called FluView. During the week of January 31 – February 6, 2010, most key flu indicators remained about the same as during the previous week. Below is a summary of the most recent key indicators:

• Visits to doctors for influenza-like illness (ILI) nationally increased slightly over last week but remain low overall. The national increase in ILI was driven by elevated ILI in 3 of 10 U.S. regions. Regions 4, 7, and 9 reported ILI slightly higher than average for the United States. Region 4 is comprised of Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina and Tennessee. Region 7 is comprised of Iowa, Kansas, Missouri and Nebraska, and region 9 is comprised of Arizona, California, Hawaii and Nevada.
• Very few 2009 H1N1 laboratory-confirmed hospitalizations were reported by states during the week ending February 6 for most age groups.
• The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report decreased over the previous week and is now lower than expected for this time of year. In addition, another three flu-related pediatric deaths were reported this week: two of these deaths were associated with laboratory confirmed 2009 H1N1, and one death was associated with an influenza A virus for which the subtype was undetermined. Since April 2009, CDC has received reports of 324 laboratory-confirmed pediatric deaths: 274 due to 2009 H1N1, 48 pediatric deaths that were laboratory confirmed as influenza, but the flu virus subtype was not determined, and two pediatric deaths that were associated with seasonal influenza viruses. (Laboratory-confirmed deaths are thought to represent an undercount of the actual number. CDC has providedestimates about the number of 2009 H1N1 cases and related hospitalizations and deaths.)
• No states reported widespread influenza activity. Six states reported regional influenza activity. They are: Alabama, Georgia, Maine, New Jersey, New Mexico, and South Carolina.

Almost all of the influenza viruses identified so far continue to be 2009 H1N1 influenza A viruses. These viruses remain similar to the virus chosen for the 2009 H1N1 vaccine, and remain susceptible to the antiviral drugs oseltamivir and zanamivir with rare exception.