Key Flu Indicators

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 August 16-22, 2009, a review of these key indictors found that influenza activity is either stable, or is increasing in some areas. Activity appears to be increasing in the Southeast based on influenza-like illness data reported by health care providers. Below is a summary of the most recent key indicators:

• Visits to doctors for influenza-like illness (ILI) were highest in February during the 2008-09 flu season, but rose again in April 2009 after the new H1N1 virus emerged. Current visits to doctors for influenza-like illness are down from April, but are higher than what is expected in the summer and has increased over the last two weeks.
• Total influenza hospitalization rates for adults and children are similar to or lower than seasonal influenza hospitalization rates depending on age group.
• The proportion of deaths attributed to pneumonia and influenza (P&I) was low and within the bounds of what is expected in the summer.
• Most state health officials are reporting regional or sporadic influenza activity. Two states (Alaska and Georgia) and Puerto Rico are reporting widespread influenza activity at this time. Any reports of widespread influenza activity in August are very unusual.
• Almost all of the influenza viruses identified were the new 2009 H1N1 influenza A viruses. These 2009 H1N1 viruses remain similar to the viruses chosen for the 2009 H1N1 vaccine and remain susceptible to antiviral drugs (oseltamivir and zanamivir) with rare exception.