2009 H1N1 Flu: Situation Update

Key Flu Indicators

March 19, 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 March 7-13, 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 remained stable and ILI remains low nationally. ILI is also looked at by region, and one of 10 U.S. regions is reporting elevated ILI. Elevated ILI was seen in region 4. Region 4 is comprised of Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee.
• Laboratory-confirmed hospitalizations rates have leveled off and very few hospitalizations were reported by states during the week ending March 13.
• The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report decreased over last week and in general remains low. Two flu-related pediatric deaths were reported this week. One death was associated with 2009 H1N1 virus infection and the remaining death was associated with an influenza A virus for which the subtype was undetermined. Since April 2009, CDC has received reports of 331 laboratory-confirmed pediatric deaths: 278 due to 2009 H1N1, 51 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. Three states reported regional influenza activity. They are: Alabama, Georgia and Mississippi.
• 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