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

2011-2012 Influenza Season Week 41 ending October 15, 2011


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

Synopsis:

During week 41 (October 9-15, 2011), influenza activity remained low in the United States.

  • Viral Surveillance: Of the 1,286 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division, 6 (0.5%) were positive for influenza.
  • Novel influenza A Virus: One human infection with a novel influenza A virus was reported.
  • Pneumonia and Influenza (P&I) Mortality Surveillance: The proportion of deaths attributed to P&I was below the epidemic threshold.
  • Influenza-associated Pediatric Mortality: No influenza-associated pediatric deaths were reported
  • Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 1.0%, which is below the national baseline of 2.4%. All 10 regions reported ILI below region-specific baseline levels. Forty-nine states and New York City experienced minimal ILI activity and the District of Columbia and one state had insufficient data.
  • Geographic Spread of Influenza: The geographic spread of influenza in the District of Columbia, Guam, Puerto Rico, the U.S. Virgin Islands, and 18 states was reported as sporadic and 32 states reported no influenza activity.

National and Regional Summary of Select Surveillance Components

HHS Surveillance Regions* Data for week 41 Data cumulative since October 2, 2011 (Week 40)
Outpatient ILI† % positive for flu‡ Number of jurisdictions reporting regional or widespread activity§ A (H3) A (2009 H1N1) A(Subtyping not performed) B Pediatric Deaths
Nation Normal 1.5% 0 of 54 13 3 9 5 0
Region 1 Normal 5.6% 0 of 6 0 0 0 3 0
Region 2 Normal 0.6% 0 of 4 0 0 0 0 0
Region 3 Normal 1.1% 0 of 6 0 0 1 0 0
Region 4 Normal 2.0% 0 of 8 0 0 5 1 0
Region 5 Normal 2.2% 0 of 6 4 1 0 1 0
Region 6 Normal 0.2% 0 of 5 1 0 1 0 0
Region 7 Normal 0.0% 0 of 4 0 0 0 0 0
Region 8 Normal 0.6% 0 of 6 2 0 2 0 0
Region 9 Normal 1.7% 0 of 5 4 2 0 0 0
Region 10 Normal 2.2% 0 of 4 2 0 0 0 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 and Washington D.C. report to CDC the number of respiratory specimens tested for influenza and the number positive by influenza type and subtype. The results of tests performed during the current week are summarized in the table below.

Week 41
No. of specimens tested 1,286
No. of positive specimens (%) 6 (0.5%)
Positive specimens by type/subtype
  Influenza A 4 (67%)
             A (2009 H1N1) 0 (0.0%) 
             A (subtyping not performed) 0 (0.0%) 
             A (H3) 4 (100%) 
  Influenza B 2 (33%)

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


Novel Influenza A Virus:

One case of human infection with a novel influenza A virus was reported by the Maine Center for Disease Control and Prevention. The patient was infected with a swine origin influenza A (H3N2) virus. Testing performed at Maine’s Health and Environmental Testing Laboratory on October 14, 2011 indicated a likely swine origin influenza A (H3N2) virus and this result was confirmed at CDC on October 16, 2011. The patient reported attendance at an event where pigs were present in the week preceding symptom onset on October 7, 2011, did not require hospitalization, and continues to recover. No illness has been identified in family members or close contacts, but the investigation is ongoing.

Swine-origin triple reassortant Influenza A (H3N2) viruses have been circulating among North American swine herds since the late 1990's. Human infections with these viruses are detected sporadically, and cases usually occur following direct or indirect contact with pigs. Thirteen human cases of swine-origin influenza A (H3N2) have been reported to CDC since 2005, including five this year. No epidemiologic link has been identified between the case in Maine and recent cases reported in Indiana and Pennsylvania. General information about swine influenza is available at http://www.cdc.gov/flu/swineflu/

Antigenic Characterization:

No antigenic characterization data is available for specimens collected after October 1, 2011. However, the vast majority of the isolates collected from May – September 2010 were closely related antigenically to the 2009 influenza A (H1N1), influenza A (H3N2), and influenza B components of the 2011-12 influenza vaccine.

Antiviral Resistance:

Testing of 2009 influenza A (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 influenza A (H1N1) clinical samples are tested for a single known mutation in the neuraminidase of the virus that confers oseltamivir resistance (H275Y). The data summarized below combine the results of both test methods. These samples are routinely obtained for surveillance purposes rather than for diagnostic testing of patients with suspected antiviral resistance.

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 of the sustained high levels of resistance, data from adamantane resistance testing are not presented in the table below.

Oseltamivir Zanamivir
Virus Samples tested (n) Resistant Viruses, Number (%) Virus Samples tested (n) Resistant Viruses, Number (%)
Influenza A (H3N2) 1 0 (0.0) 1 0 (0.0)
Influenza B 1 0 (0.0) 1 0 (0.0)
2009 Influenza A (H1N1) 0 0 (0.0) 0 0 (0.0)

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 influenza A (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 influenza-related complications. Additional information on recommendations for treatment and chemoprophylaxis of influenza virus infection with antiviral agents is available at (http://www.cdc.gov/flu/antivirals/index.htm).

Pneumonia and Influenza (P&I) Mortality Surveillance

During week 41, 6.4% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.6% for week 41.

Pneumonia And Influenza Mortality
View Full Screen | View PowerPoint Presentation


Influenza-Associated Pediatric Mortality

No influenza-associated pediatric deaths were reported to CDC during week 41.


Influenza-Associated Pediatric Mortality
View Full Screen | View PowerPoint Presentation


Influenza-Associated Hospitalizations

The Influenza Hospitalization Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza related hospitalizations in children (persons younger than 18 years) and adults. The network covers more than 80 counties in the 10 Emerging Infections Program (EIP) states (CA, CO, CT, GA, MD, MN, NM, NY, OR, and TN) and four additional states (MI, OH, RI and UT). FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

Outpatient Illness Surveillance:

Nationwide during week 41, 1.0% 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 2.4%. (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 0.6% to 1.7% during week 41. All 10 regions reported a proportion of outpatient visits for ILI below their region-specific baseline levels.


ILINet State 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 spring and fall 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 intense, which would correspond to ILI activity from outpatient clinics being much higher than average.

During week 41, the following ILI activity levels were experienced:

  • Forty-nine states and New York City experienced minimal ILI activity (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, 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)./li>
  • Data were insufficient to calculate an ILI activity level from the District of Columbia and one state (Idaho).

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 are 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 41, the following influenza activity was reported:

  • Sporadic influenza activity was reported by the District of Columbia, Guam, Puerto Rico, the U.S. Virgin Islands, and 18 states (Alaska, Arkansas, California, Connecticut, Florida, Hawaii, Indiana, Louisiana, Maine, Massachusetts, Michigan, Minnesota, New York, Ohio, Pennsylvania, Virginia, Washington, and Wisconsin).
  • No influenza activity was reported by 32 states (Alabama, Arizona, Colorado, Delaware, Georgia, Idaho, Illinois, Iowa, Kansas, Kentucky, Maryland, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, North Carolina, North Dakota, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, West Virginia, and Wyoming).

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

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

Alabama

Alaska

Arizona

Arkansas

California

Colorado

Connecticut

Delaware

District of Columbia

Florida

Georgia

Hawaii

Idaho

Illinois

Indiana

Iowa

Kansas

Kentucky

Louisiana

Maine

Maryland

Massachusetts

Michigan

Minnesota

Mississippi

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

Wyoming

New York City

Virgin Islands

Distribute Project: Additional information on the Distribute syndromic surveillance project, developed and piloted by the International Society for Disease Surveillance (ISDS) now working in collaboration with CDC, to enhance and support Emergency Department (ED) surveillance, is available at http://isdsdistribute.org/

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 http://www.google.org/flutrends/

Europe: for the most recent influenza surveillance information from Europe, please see WHO/Europe at http://www.euroflu.org/index.php and visit the European Centre for Disease Prevention and Control at http://ecdc.europa.eu/en/publications/surveillance_reports/influenza/Pages/weekly_influenza_surveillance_overview.aspx

Public Health Agency of Canada: The most up-to-date influenza information from Canada is available at http://www.phac-aspc.gc.ca/fluwatch/

World Health Organization FluNet: Additional influenza surveillance information from participating WHO member nations is available at http://www.who.int/influenza/gisrs_laboratory/flunet/en/index.html

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A description of surveillance methods is available at: http://www.cdc.gov/flu/weekly/overview.htm

 
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