Key Flu Indicators

March 5, 2010, 11:00 AM

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 February 21 -27, 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 decreased again this week over last week and remain low. ILI is also looked at by region and two of 10 U.S. regions are reporting elevated ILI. Elevated ILI was seen in regions 4 and 9. Region 4 is comprised of Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee. And region 9 is comprised of Arizona, California, Hawaii and Nevada.
• Laboratory-confirmed hospitalizations rates have leveled off and very few hospitalizations were reported by states during the week ending February 27.
• The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report increased very slightly over last week but remains low. One flu-related pediatric death was reported this week associated with an influenza B virus infection that occurred in February 2009. Since April 2009, CDC has received reports of 329 laboratory-confirmed pediatric deaths: 277 due to 2009 H1N1, 50 pediatric deaths that were laboratory confirmed as influenza A, 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 provided estimates about the number of 2009 H1N1 cases and related hospitalizations and deaths.
• No states reported widespread influenza activity. Four states reported regional influenza activity. They are: Alabama, Georgia, Mississippi and South Carolina.
• The majority 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. Some influenza B viruses are circulating at low levels, and these viruses remain similar to the influenza B virus component of the 2009-10 seasonal flu vaccine.

*All data are preliminary and may change as more reports are received.

More on the Situation

• Influenza Surveillance in the United States
  Links to information related to U.S. Influenza Surveillance
• CDC Response
  A summary of CDC activities
• FluView
  A Weekly Influenza Surveillance Report Prepared by the Influenza Division.
• International Situation Update
  A summary of global 2009 H1N1 activity.
  
• Facts and Figures
  A summary of key 2009 H1N1 disease characteristics.
• Health Alert Network (HAN) Messages
• Q & A: CDC's Online Reporting

Background

• Background
  Learn about the emergence of the 2009 H1N1 virus in the United States and WHO's declaration of a novel H1N1 pandemic.
• Past Situation Updates
• Press Updates
• Other Reports and Publications