2009 H1N1 Flu: Situation Update

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 September 6-12, 2009, a review of the key indictors found that influenza activity continued to increase in the United States compared to the prior weeks. Below is a summary of the most recent key indicators:

• Visits to doctors for influenza-like illness (ILI) are increasing nationally. Visits to doctors for influenza-like illness are higher than what is expected during this time of year and have increased for five consecutive weeks now. This is very unusual for this time of year.
• Total influenza hospitalization rates for adults and children are similar to or lower than seasonal influenza hospitalization rates depending on age group, but are higher than expected for this time of year.
• The proportion of deaths attributed to pneumonia and influenza (P&I) was low and within the bounds of what is expected at this time of year.
• Twenty-one states are reporting widespread influenza activity at this time. They are: Alabama, Alaska, Arizona, Arkansas, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Mississippi, Nevada, New Mexico, North Carolina, Oklahoma, Pennsylvania, South Carolina, Tennessee, and Virginia. Any reports of widespread influenza activity in September are very unusual.
• Almost all of the influenza viruses identified so far are 2009 H1N1 influenza A viruses. These viruses remain similar to the viruses chosen for the 2009 H1N1 vaccine, and remain susceptible to the antiviral drugs oseltamivir and zanamivir with rare exceptions.