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FluView: A Weekly Influenza Surveillance Report Prepared by the Influenza Division

2013-2014 Influenza Season Week 44 ending November 2, 2013

All data are preliminary and may change as more reports are received.


During week 44 (October 27-November 2, 2013), influenza activity remained low in the United States.

  • Viral Surveillance: Of 4 118 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 44, 201 (4,9 %) were positive for influenza.
  • Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
  • Influenza-Associated Pediatric Deaths: Two influenza-associated pediatric deaths that occurred during the 2012-2013 season were reported.
  • Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 1,4 %, below the national baseline of 2 %. All 10 regions reported ILI below region-specific baseline levels. One state experienced moderate ILI activity, three states experienced low ILI activity, 46 states and New York City experienced minimal ILI activity and the District of Columbia had insufficient data.
  • Geographic Spread of Influenza: The geographic spread of influenza in two states was reported as regional; Puerto Rico and 4 states reported local influenza activity; the District of Columbia, Guam and 34 states reported sporadic influenza activity; 10 states reported no influenza activity, and the U.S. Virgin Islands did not report.

A description of surveillance methods is available at:

National and Regional Summary of Select Surveillance Components

HHS Surveillance Regions* Data for current week Data cumulative since September 29, 2013 (Week 40)
Out-patient ILI† % positive for flu‡ Number of jurisdictions reporting regional or widespread activity§ 2009 H1N1 A (H3) A(Subtyping not performed) B Pediatric Deaths
Nation Normal 4,9 % 2 of 54 248 75 510 125 0
Region 1 Normal 0,7 % 0 of 6 3 1 1 0 0
Region 2 Normal 1,2 % 0 of 4 17 3 3 2 0
Region 3 Normal 0,8 % 0 of 6 11 4 0 1 0
Region 4 Normal 9,7 % 1 of 8 128 1 448 83 0
Region 5 Normal 2,6 % 0 of 6 16 11 2 5 0
Region 6 Normal 1,3 % 0 of 5 15 8 10 5 0
Region 7 Normal 0,8 % 0 of 4 4 0 0 9 0
Region 8 Normal 2,7 % 0 of 6 27 9 22 11 0
Region 9 Normal 3 % 0 of 5 25 27 12 6 0
Region 10 Normal 3,4 % 1 of 4 2 11 12 3 0

*HHS regions (Region 1 CT, ME, MA, NH, RI, VT; Region 2: NJ, NY, Puerto Rico, US Virgin Islands; Region 3: DE, DC, MD, PA, VA, WV; Region 4: AL, FL, GA, KY, MS, NC, SC, TN; Region 5: IL, IN, MI, MN, OH, WI; Region 6: AR, LA, NM, OK, TX; Region 7: IA, KS, MO, NE; Region 8: CO, MT, ND, SD, UT, WY; Region 9: AZ, CA, Guam, HI, NV; and Region 10: AK, ID, OR, WA).
† Elevated means the % of visits for ILI is at or above the national or region-specific baseline
‡ National data are for current week; regional data are for the most recent three weeks
§ Includes all 50 states, the District of Columbia, Guam, Puerto Rico, and U.S. Virgin Islands

U.S. Virologic Surveillance

WHO and NREVSS collaborating laboratories located in all 50 states, Puerto Rico, and Washington D.C. report to CDC the number of respiratory specimens tested for influenza and the number positive by influenza virus type and influenza A virus subtype. The results of tests performed during the current week are summarized in the table below.

Region specific data can be found at

Week 44
No. of specimens tested 4 118
No. of positive specimens (%) 201 (4,9 %)
Positive specimens by type/subtype
  Influenza A 167 (83,1 %)
             2009 H1N1 43 (25,7 %) 
              H3 19 (11,4 %) 
            Subtyping not performed 105 (62,9 %) 
  Influenza B 34 (16,9 %)

INFLUENZA Virus Isolated
View National and Regional Level Graphs and Data | View Chart Data | View Full Screen | View PowerPoint Presentation

Antigenic Characterization*

CDC has antigenically characterized four influenza viruses [three 2009 H1N1 viruses and one influenza B virus] collected by U.S. laboratories since October 1, 2013 by hemagglutination inhibition (HI).

2009 H1N1 [3]:

  • All three 2009 H1N1 viruses tested were characterized as A/California/7/2009-like, the influenza A (H1N1) component of the 2013-2014 Northern Hemisphere influenza vaccine.

Influenza B (B/Yamagata and B/Victoria lineages) [1]:

  • Yamagata Lineage [1]: The one influenza B virus tested was characterized as B/Massachusetts/02/2012-like, which is included as an influenza B component in both the 2013-2014 Northern Hemisphere trivalent and quadrivalent influenza vaccines.

*For more information see the section on antigenic characterization in the MMWR “Update: Influenza Activity — United States and Worldwide, May 19–September 28, 2013”.

Antiviral Resistance

Testing of 2009 H1N1, influenza A (H3N2), and influenza B virus isolates for resistance to neuraminidase inhibitors (oseltamivir and zanamivir) is performed at CDC using a functional assay. Additional 2009 H1N1 and influenza A (H3N2) clinical samples are tested for mutations of the virus known to confer oseltamivir resistance. The data summarized below combine the results of both testing methods. These samples are routinely obtained for surveillance purposes rather than for diagnostic testing of patients suspected to be infected with antiviral-resistant virus.

High levels of resistance to the adamantanes (amantadine and rimantadine) persist among 2009 influenza A (H1N1) and A (H3N2) viruses (the adamantanes are not effective against influenza B viruses). As a result, data from adamantane resistance testing are not presented below.

Neuraminidase Inhibitor Resistance Testing Results on Samples Collected Since October 1, 2013

Oseltamivir Zanamivir
Virus Samples tested (n) Resistant Viruses, Number (%) Virus Samples tested (n) Resistant Viruses, Number (%)
Influenza A (H3N2) 6 0 (0.0) 6 0 (0.0)
Influenza B 1 0 (0.0) 1 0 (0.0)
2009 H1N1 37* 2 (5.4) 31 0 (0.0)

*Includes specimens tested in national surveillance and additional specimens tested at public health laboratories in two states (AZ and MI) who share testing results with CDC.

The majority of currently circulating influenza viruses are susceptible to the neuraminidase inhibitor antiviral medications oseltamivir and zanamivir; however, rare sporadic cases of oseltamivir-resistant 2009 H1N1 and A (H3N2) viruses have been detected worldwide. Antiviral treatment with oseltamivir or zanamivir is recommended as early as possible for patients with confirmed or suspected influenza who have severe, complicated, or progressive illness; who require hospitalization; or who are at greater risk for serious influenza-related complications. Additional information on recommendations for treatment and chemoprophylaxis of influenza virus infection with antiviral agents is available at

Pneumonia and Influenza (P&I) Mortality Surveillance

During week 44, 5,3 % of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6,3 % for week 44.

Pneumonia And Influenza Mortality
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Influenza-Associated Pediatric Mortality

Two influenza-associated pediatric deaths that occurred during the 2012-2013 season were reported to CDC during week 44; one was associated with an influenza A (H3) virus and one was associated with an influenza A virus for which no subtyping was performed. These deaths bring the total number of reported pediatric deaths for that season to 169. No influenza-associated pediatric deaths for the 2013-2014 season have been reported to CDC.

Additional data can be found at

Click on image to launch interactive tool

View Interactive Application | View Full Screen | View PowerPoint Presentation

Influenza-Associated Hospitalizations

The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts all age population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in the Emerging Infections Program (EIP) states and Influenza Hospitalization Surveillance Project (IHSP) states. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season. Additional FluSurv-NET data can be found at: and

Outpatient Illness Surveillance

Nationwide during week 44, 1,4 % of patient visits reported through the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) were due to influenza-like illness (ILI). This percentage is below the national baseline of 2 %. (ILI is defined as fever (temperature of 100°F [37.8°C] or greater) and cough and/or sore throat.)

national levels of ILI and ARI
View National and Regional Level Graphs and Data | View Chart Data | View Full Screen | View PowerPoint Presentation

On a regional level, the percentage of outpatient visits for ILI ranged from 0,4 % to 2,6 % during week 44. All 10 regions reported a proportion of outpatient visits for ILI below their region-specific baseline levels.

Region specific data is available at

ILINet Activity Indicator Map

Data collected in ILINet are used to produce a measure of ILI activity* by state. Activity levels are based on the percent of outpatient visits in a state due to ILI and are compared to the average percent of ILI visits that occur during weeks with little or no influenza virus circulation. Activity levels range from minimal, which would correspond to ILI activity from outpatient clinics being below the average, to high, which would correspond to ILI activity from outpatient clinics being much higher than average.

During week 44, the following ILI activity levels were experienced:

  • One state experienced moderate ILI activity (Mississippi)
  • Three states experienced low ILI activity (Arkansas, Kentucky, and Louisiana).
  • Forty-six states and New York City experienced minimal ILI activity (Alabama, Alaska, Arizona, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming).
  • Data were insufficient to calculate an ILI activity level from the District of Columbia.

Click on map to launch interactive tool


Click on map to launch interactive tool

*This map uses the proportion of outpatient visits to health care providers for influenza-like illness to measure the ILI activity level within a state. It does not, however, measure the extent of geographic spread of flu within a state. Therefore, outbreaks occurring in a single city could cause the state to display high activity levels.
Data collected in ILINet may disproportionately represent certain populations within a state, and therefore, may not accurately depict the full picture of influenza activity for the whole state.
Data displayed in this map are based on data collected in ILINet, whereas the State and Territorial flu activity map is based on reports from state and territorial epidemiologists. The data presented in this map is preliminary and may change as more data is received.
Differences in the data presented here by CDC and independently by some state health departments likely represent differing levels of data completeness with data presented by the state likely being the more complete.

Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists

The influenza activity reported by state and territorial epidemiologists indicates geographic spread of influenza viruses, but does not measure the severity of influenza activity.

During week 44, the following influenza activity was reported:

  • Regional influenza activity was reported by two states (Alaska and Alabama).
  • Local influenza activity was reported by Puerto Rico and four states (Mississippi, South Carolina, Texas, and Virginia).
  • Sporadic influenza activity was reported by the District of Columbia, Guam, and 34 states (Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, Nevada, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Utah, Washington, Wisconsin, and Wyoming).
  • No influenza activity was reported by 10 states (Delaware, Idaho, Illinois, Missouri, Montana, New Hampshire, Rhode Island, Tennessee, Vermont, and West Virginia).
  • The U.S. Virgin Islands did not report.

U. S. Map for Weekly Influenza Activity

Flu Activity data in XML Format | View Full Screen

View Full Screen

Additional National and International Influenza Surveillance Information

FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics. To access these tools visit

U.S. State and local influenza surveillance: Click on a jurisdiction below to access the latest local influenza information.









District of Columbia





















New Hampshire

New Jersey

New Mexico

New York

North Carolina

North Dakota





Rhode Island

South Carolina

South Dakota







West Virginia



New York City

Virgin Islands

Google Flu Trends: Google Flu Trends uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from the U.S. and worldwide, see

World Health Organization: Additional influenza surveillance information from participating WHO member nations is available through FluNet and the Global Epidemiology Reports.

WHO Collaborating Centers for Influenza located in Australia, China, Japan, and the United Kingdom.

Europe: for the most recent influenza surveillance information from Europe, please see WHO/Europe at and visit the European Centre for Disease Prevention and Control at

Public Health Agency of Canada: The most up-to-date influenza information from Canada is available at

Health Protection Agency (United Kingdom): The most up-to-date influenza information from the United Kingdom is available at

Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.


A description of surveillance methods is available at:

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