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Situation Update: Summary of Weekly FluView Report

Key Flu Indicators

According to the FluView report for the week ending January 7, 2017 (week 1), flu activity remains elevated in the United States. The proportion of people seeing their health care provider for influenza-like-illness (ILI) has been at or above the national baseline for four consecutive weeks so far this season and the number of states reporting widespread flu activity increased from 12 states to 21 states. Also, CDC reported the first three flu-associated pediatric deaths for the 2016-2017 season. Influenza A (H3) viruses continue to predominate. Flu activity is expected to continue over the coming weeks. CDC recommends annual flu vaccination for everyone 6 months of age and older. Anyone who has not gotten vaccinated yet this season should get vaccinated now. Below is a summary of the key flu indicators for the week ending January 7, 2017:

  • Influenza-like Illness Surveillance: For the week ending January 7, the proportion of people seeing their health care provider for influenza-like illness (ILI) was 3.2%. This remains above the national baseline of 2.2%. All ten regions reported ILI at or above their region-specific baseline level. For the last 15 seasons, the average duration of a flu season by this measure has been 13 weeks, with a range from one week to 20 weeks.
  • Influenza-like Illness State Activity Indicator Map: New York City, Puerto Rio, and eight states (Arizona, Georgia, Missouri, New Jersey, New York, Oklahoma, Oregon, and South Carolina) experienced high ILI activity. Six states (Alabama, California, Louisiana, Nevada, Pennsylvania, and Virginia) experienced moderate ILI activity.  Seven states (Colorado, Hawaii, Illinois, Kansas, Michigan, Mississippi, and Tennessee) experienced low ILI activity. 28 states experienced minimal ILI activity. The District of Columbia and one state (Utah) 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.
  • Geographic Spread of Influenza Viruses: Widespread influenza activity was reported by Puerto Rico and 21 states (Alaska, California, Connecticut, Delaware, Idaho, Kentucky, Maryland, Massachusetts, Montana, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, Virginia, and Washington).  Regional influenza activity was reported by Guam and 21 states (Alabama, Arizona, Arkansas, Colorado, Florida, Hawaii, Indiana, Louisiana, Maine, Michigan, Minnesota, Mississippi, Missouri, Nevada, North Dakota, South Carolina, South Dakota, Texas, Utah, Wisconsin, and Wyoming). Local flu activity was reported by the District of Columbia and eight states (Georgia, Illinois, Iowa, Kansas, New Mexico, Tennessee, Vermont, and West Virginia). The U.S. Virgin Islands reported no flu activity. Geographic spread data show how many areas within a state or territory are seeing flu activity.
  • Flu-Associated Hospitalizations: Since October 1, 2016, a total of 1,992 laboratory-confirmed influenza-associated hospitalizations have been reported. This translates to a cumulative overall rate of 7.1 hospitalizations per 100,000 people in the United States. Additional data, including hospitalization rates during other influenza seasons, can be found at http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html and http://gis.cdc.gov/grasp/fluview/FluHospChars.html
    • The highest hospitalization rates are among people 65 years and older (32.4 per 100,000), followed by adults 50-64 years (7.1 per 100,000) and children younger than 5 years (4.8 per 100,000). During most seasons, children younger than 5 years and adults 65 years and older have the highest hospitalization rates.
      • Hospitalization data are collected from 13 states representing approximately 9% of the total U.S. population. The number of hospitalizations reported does not reflect the actual total number of influenza-associated hospitalizations in the United States.
  • Mortality Surveillance:
    • The proportion of deaths attributed to pneumonia and influenza (P&I) was 6.2% for the week ending December 24, 2016 (week 51). This percentages is below the epidemic threshold of 7.2% for week 51 in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
  • Pediatric Deaths:
    • Three influenza-associated pediatric deaths were reported to CDC during the week ending January 7, 2017.
    • One death was associated with an influenza A (H3) virus and occurred during week 51 (the week ending December 24, 2016).
    • One death was associated with an influenza A virus for which no subtyping was performed and occurred during week 52 (the week ending December 31, 2016).
    • One death was associated with an influenza B virus and occurred during week 51.
    • A total of 3 influenza-associated pediatric deaths have been reported during the 2016-2017 season.
  • Laboratory Data:
    • Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending January 7 was 13.9%.
    • Regionally, the three week average percent of specimens testing positive for influenza in clinical laboratories ranged from 7.2% to 29.8%.
    • During the week ending January 7, of the 3,580 influenza-positive tests reported to CDC by clinical laboratories, 3,287 (91.8%) were influenza A viruses and 293 (8.2%) were influenza B viruses.
    • The most frequently identified influenza virus type reported by public health laboratories during the week ending January 7 was influenza A viruses, with influenza A (H3) viruses predominating. 
    • During the week ending January 7, 885 (95.4%) of the 928 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 43 (4.6%) were influenza B viruses. Of the 854 influenza A viruses that were subtyped, 833 (97.5%) were H3 viruses and 21 (2.5%) were (H1N1)pdm09 viruses.
    • Since October 1, 2016, antigenic and/or genetic characterization shows that the majority of the tested viruses remain similar to the recommended components of the 2016-2017 Northern Hemisphere vaccines.
    • Since October 1, 2016, CDC tested 449 specimens (51 influenza A (H1N1)pdm09, 317 influenza A (H3N2), and 81 influenza B viruses) for resistance to the neuraminidase inhibitors antiviral drugs. None of the tested viruses were found to be resistant to oseltamivir, zanamivir, or peramivir.
  • 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 2016-2017 season can be found on the current FluView.

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