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Situation Update: Summary of Weekly FluView

Key Flu Indicators

According to this week’s FluView report, overall seasonal influenza activity remains low across the United States. Flu activity is expected to increase in the coming weeks. People who have not already gotten a flu vaccine for the 2014-2015 season should do so now. Below is a summary of the key flu indicators for the week ending October 25, 2014:

  • For the week ending October 25, the proportion of people seeing their health care provider for influenza-like illness (ILI) was below the national baseline. All 10 U.S. regions reported ILI activity below region-specific baseline levels.
  • One state (Florida) experienced low ILI activity. Puerto Rico, New York City and 49 states, experienced minimal ILI activity. The District of Columbia did not have sufficient data to calculate an activity level. ILI activity data indicate the amount of flu-like illness that is occurring in each state.
  • Guam reported widespread geographic influenza activity. One state (Alaska) reported regional influenza activity. Puerto Rico and eight states (Connecticut, Florida, Maryland, Massachusetts, New Hampshire, Oregon, Texas, and Utah) reported local activity. The U.S. Virgin Islands and 32 states reported sporadic influenza activity. The District of Columbia and nine states reported no influenza activity. Geographic spread data show how many areas within a state or territory are seeing flu activity.
  • Data regarding influenza-associated hospitalizations for the 2014-2015 influenza season is not yet available for this season.
  • The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Mortality Reporting System is below the epidemic threshold.
  • No influenza-associated pediatric deaths were reported to CDC during the week ending October 25. One influenza-associated pediatric death has been reported for the 2014-2015 season and occurred during the week ending October 4, 2014.
  • Nationally, the percentage of respiratory specimens testing positive for influenza viruses in the United States during the week ending October 25 was 4.3%. For the most recent three weeks, the regional percentage of respiratory specimens testing positive for influenza viruses ranged from 1.2% to 8.2%.
  • Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. During the week ending October 25, 237 (74.1%) of the 320 influenza-positive tests reported to CDC were influenza A viruses and 83 (25.9%) were influenza B viruses. Of the 82 influenza A viruses that were subtyped, 96% were H3 viruses and 4% were 2009 H1N1 viruses.
  • CDC has antigenically characterized 10 influenza A (H3N2) viruses collected since October 1, 2014. This is the first antigenic characterization data available for H3N2 viruses collected in the United States since October 1, 2014.
    • Seven (70%) of the 10 influenza A (H3N2) viruses tested have been characterized as A/Texas/50/2012-like. This is the influenza A (H3N2) component of the 2014-2015 Northern Hemisphere influenza vaccine. Three (30%) H3N2 viruses were antigenically similar to A/Switzerland/9715293/2013, the H3N2 virus selected for the 2015 Southern Hemisphere influenza vaccine.
  • No antiviral resistance data is available for specimens collected after October 1, 2014.

FluView is available – and past issues are archived – on the CDC website.

Note: Delays in reporting may mean that data changes over time. The most up to date data for all weeks during the 2014-2015 season can be found on the current FluView.

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