Situation Update: Summary of Weekly FluView
Key Flu Indicators
Influenza activity is increasing in the United States. This week's FluView reports the national percentage of respiratory specimens testing positive for influenza was 15.5 percent. This is the second consecutive week this number has been above 10 percent; generally a marker to indicate that flu season is beginning. In addition, California reported widespread influenza activity for the second week in a row, and a third pediatric death was reported for the season. Influenza-like-illness (ILI) remains relatively low nationally, but one region of the county reported ILI above baseline. Further increases in activity are expected in the coming weeks. Below is a summary of the most recent key indicators:
- Visits to doctors for influenza-like illness (ILI) nationally remained below the baseline this week, but 1 of the 10 U.S. regions (Region 7) reported ILI activity above region-specific baseline levels (a decrease from 2 regions last week). Region 7 includes Iowa, Kansas, Missouri and Nebraska.
- One state reported widespread influenza activity (the same number as last week). Regional influenza activity was reported by 12 states (an increase from 9 states last week). Seventeen states reported local influenza activity (an increase from 12 states last week). Twenty states (a decrease from 27 states last week), the District of Columbia, and Guam reported sporadic influenza activity. Only the U.S. Virgin Islands reported no influenza activity. Puerto Rico did not report.
- Hospitalization rates for patients with laboratory-confirmed influenza, based on FluSurv-NET, are lower than the rates reported at this time during previous influenza seasons.
- The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Mortality Reporting System decreased from the previous report, and is below the level expected for this time of year.
- One influenza-associated pediatric death associated with an influenza B virus infection was reported this week. This is the third influenza-associated pediatric death reported thus far for the 2011-2012 season.
- Nationally, the percentage of specimens testing positive for influenza in the United States was 15.5%, an increase from last week (12.6%). All regions saw increases in the percent of specimens testing positive from the previous week (except Region 10, which stayed the same), but there are regional differences in current virus activity.
- Influenza viruses identified so far include 2009 H1N1 viruses, influenza A (H3N2) viruses and influenza B viruses. Nationally influenza A (H3N2) viruses predominate, however in the past several weeks the proportion of 2009 H1N1 viruses has been increasing. In addition, regional differences exist. For example, over the past several weeks 2009 H1N1 viruses have been most commonly reported in Region 6 (the south central region of the country), while H3N2 virus predominate by far in Regions 5 and 8.
- Though few viruses have been available for testing so far this season, all isolates tested remain susceptible to the antiviral drugs oseltamivir and zanamivir.
FluView is available – and past issues are archived – on the CDC website.
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