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 November 22-28, 2009, influenza activity decreased across all key indicators over the previous week, but most indicators remain higher than normal for this time of year. 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. This is the fifth consecutive week of national decreases in ILI after four consecutive weeks of sharp increases. Eight of ten regions continue to report ILI activity above what is expected for this time of year. Two regions (Region 6 and Region 10) are reporting little ILI activity. While ILI has declined, visits to doctors for influenza-like illness still remain elevated nationally.
- Influenza hospitalization rates have decreased across all age groups but remain higher than expected for this time of year. Though declining, hospitalization rates continue to be highest in children 0-4 years old.
- The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report declined over the previous week, but continues to be higher than expected for this time of year. This is the ninth consecutive week that the proportion of deaths attributed to pneumonia and influenza (P&I) has been above the epidemic threshold. In addition, 17 flu-related pediatric deaths were reported this week: 12 of these deaths were associated with laboratory confirmed 2009 H1N1 and 5 were associated with influenza A viruses, but were not subtyped. Since April 2009, CDC has received reports of 251 laboratory-confirmed pediatric deaths: 210 due to 2009 H1N1, 40 pediatric deaths that were laboratory confirmed as influenza, but the flu virus subtype was not determined, and one pediatric death associated with a seasonal influenza virus. (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.
- Twenty-five states are reporting widespread influenza activity; a decline of 7 states from last week. They are: Alabama, Alaska, Arizona, California, Connecticut, Delaware, Florida, Indiana, Kentucky, Maine, Maryland, Massachusetts, Michigan, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Utah, Vermont, and Virginia. Seventeen states are reporting regional influenza activity, the District of Columbia, Puerto Rico and six states reported local influenza activity, and Guam, the U.S. Virgin Islands and two states reported sporadic influenza activity.
- 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.
- All data are preliminary and may change as more reports are received.