Latest CDC H1N1 Flu Update

Key Flu Indicators

November 20, 2009, 2:30 PM
Centers for Disease Control

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 8-14, 2009, influenza activity decreased across all key indicators, but overall remained very high 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 third consecutive week of national decreases in ILI after four consecutive weeks of sharp increases. (All regions showed declines in ILI.) While ILI declined overall nationally, visits to doctors for influenza-like illness remain high.

* Influenza hospitalization rates are beginning to decline but remain higher than expected for this time of year. Hospitalization rates continue to be highest in younger populations with the highest hospitalization rate reported in children 0-4 years old.

* The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report decreased slightly but is still higher than what is expected for this time of year and has remained elevated for seven weeks now. In addition, 21 flu-related pediatric deaths were reported this week: 15 of these deaths were associated with laboratory confirmed 2009 H1N1; 6 were influenza A viruses, but were not subtyped. Since April 2009, CDC has received reports of 171 laboratory-confirmed pediatric 2009 H1N1 deaths, one influenza B death, and another 28 pediatric deaths that were laboratory confirmed as influenza, but the flu virus subtype was not determined. (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.

* Forty-three states are reporting widespread influenza activity at this time; a decline of three states from last week. They are: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, and Wisconsin.

* 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.
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