[Source: US CDC, FluView, full page: (LINK). Edited.]
2012-2013 Influenza Season Week 47 ending November 24, 2012
All data are preliminary and may change as more reports are received.
During week 47 (November 18-24, 2012), influenza activity increased in the U.S.
- Viral Surveillance: Of 5,342 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 47, 812 (15.2%) were positive for influenza.
- Novel Influenza A Virus: One human infection with a novel influenza A virus was reported.
- Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
- Influenza-associated Pediatric Deaths: No influenza-associated pediatric deaths were reported.
- Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 2.2%, which is at the national baseline of 2.2%. Five regions reported ILI above region-specific baseline levels. Five states experienced high ILI activity, two states experienced moderate ILI activity; 4 states experienced low ILI activity; New York City and 39 states experienced minimal ILI activity, and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in 4 states was reported as widespread; 7 states reported regional activity; 19 states reported local activity; the District of Columbia and 18 states reported sporadic activity; Guam and 1 state reported no influenza activity, and Puerto Rico, the U.S. Virgin Islands and 1 state did not report.
A description of surveillance methods is available at: http://www.cdc.gov/flu/weekly/overview.htm
National and Regional Summary of Select Surveillance Components
[HHS Surveillance Regions* - Data for current week: Out-patient ILI† - % positive for flu‡ - Number of jurisdictions reporting regional or widespread activity§ - Data cumulative since September 30, 2012 (Week 40): 2009 H1N1 - A (H3) - A(Subtyping not performed) – B - Pediatric Deaths]
- Nation – Elevated - 15.2% - 11 of 54 – 32 - 1,342 – 913 - 1,285 - 2
- Region 1 - Normal - 3.9% - 2 of 6 – 0 – 33 - 4 - 1 - 0
- Region 2 - Elevated - 5.0% - 1 of 4 - 3 - 58 - 48 - 59 - 0
- Region 3 – Normal - 3.8% - 0 of 6 - 4 - 66 - 7 - 15 - 0
- Region 4 - Elevated - 18.9% - 4 of 8 - 13 - 253 - 646 – 459 – 1
- Region 5 - Elevated - 20.6% - 1 of 6 - 7 - 103 - 33 - 66 - 0
- Region 6 - Elevated - 12.3% - 0 of 5 - 3 - 83 - 130 - 245 - 1
- Region 7 - Elevated - 17.1% - 1 of 4 - 0 - 209 - 6 - 162 - 0
- Region 8 - Normal - 10.0% - 0 of 6 - 1 - 116 - 13 - 238 - 0
- Region 9 - Normal - 4.3% - 0 of 5 - 0 - 122 - 23 - 21 - 0
- Region 10 - Normal - 16.0% - 2 of 4 - 1 - 299 - 3 – 19 – 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 Puerto Rico report to CDC the number of respiratory specimens tested for influenza and the number positive by influenza virus type and influenza A virus subtype. Region specific data can be found at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html. The results of tests performed during the current week are summarized in the table below.
- No. of specimens tested - 5,342
- No. of positive specimens (%) - 812 (15.2%)
- Positive specimens by type/subtype
- Influenza A - 571 (70.3%)
- 2009 H1N1 - 1 (0.2%)
- Subtyping not performed - 371 (65.0%)
- H3 - 199 (34.9%)
- Influenza B - 241 (29.7%)
- Influenza A - 571 (70.3%)
- Positive specimens by type/subtype
Novel Influenza A Virus:
One infection with an influenza A (H3N2) variant virus (H3N2v) was reported to CDC during week 47 from Iowa. While no contact with swine or other livestock in the week preceding illness was reported, investigation into potential additional sources of infection is ongoing. No further cases have been identified in contacts of the case patient. This is the first H3N2v infection reported since September 28, 2012.
A total of 311 infections with variant influenza viruses (307 H3N2v viruses, 3 H1N2v viruses, and 1 H1N1v virus) have been reported from 11 states from July 2012 through November 28, 2012. More information about H3N2v infections can be found at http://www.cdc.gov/flu/swineflu/h3n2v-outbreak.htm. The vast majority of variant virus infections have occurred after exposure to swine, though instances of likely human-to-human transmission have been identified. No ongoing human-to-human transmission has been identified. Additional information about influenza in swine, variant influenza infection in humans, and precautionary measures recommended during interactions with swine can be found at http://www.cdc.gov/flu/swineflu/index.htm.
CDC has antigenically characterized 140 influenza viruses [Two 2009 H1N1 viruses, 90 influenza A (H3N2) viruses, and 48 influenza B viruses] collected by U.S. laboratories since October 1, 2012.
2009 H1N1 :
- Both 2009 H1N1 viruses tested were characterized as A/California/7/2009-like, the influenza A (H1N1) component of the 2012-2013 influenza vaccine for the Northern Hemisphere.
Influenza A (H3N2) :
- All 90 H3N2 influenza viruses tested so far have been characterized as A/Victoria/361/2011-like, the influenza A (H3N2) component of the 2012-2013 Northern Hemisphere influenza vaccine.
Influenza B (B/Yamagata/16/88 and B/Victoria/02/87 lineages) :
- Yamagata Lineage : Thirty-four (70.8%) of the 48 influenza B viruses tested so far this season have been characterized as B/Wisconsin/1/2010-like, the influenza B component of the 2012-2013 Northern Hemisphere influenza vaccine.
- Victoria Lineage : Fourteen (29.2%) of 48 influenza B viruses tested have been from the B/Victoria lineage of viruses
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 mutation in the neuraminidase of the virus known to confer oseltamivir resistance (H275Y). 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 of the sustained high levels of resistance, data from adamantane resistance testing are not presented in the table below.
Neuraminidase Inhibitor Resistance Testing Results on Samples Collected Since October 1, 2012
[Oseltamivir: Virus Samples tested (n) - Resistant Viruses, Number (%) – Zanamivir: Virus Samples tested (n) - Resistant Viruses, Number (%)]
- Influenza A (H3N2) – 122 - 0 (0.0) – 122 - 0 (0.0)
- Influenza B – 81 - 0 (0.0) – 81 - 0 (0.0)
- 2009 H1N1 – 2 - 0 (0.0) - 2 - 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 serious 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 47, 6.3% of all deaths reported through the 122 Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.7% for week 47.
Influenza-Associated Pediatric Mortality:
No influenza-associated pediatric deaths were reported to CDC during week 47. Two influenza-associated deaths have been reported during the 2012-2013 season. Additional data can be found at: http://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html.
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: http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html.
Outpatient Illness Surveillance:
Nationwide during week 47, 2.2% 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 at the national baseline of 2.2%. (ILI is defined as fever (temperature of 100°F [37.8°C] or greater) and cough and/or sore throat.) Region specific data is available at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.
On a regional level, the percentage of outpatient visits for ILI ranged from 0.9% to 4.2% during week 47. Five regions (Regions 2, 4, 5, 6, and 7) reported a proportion of outpatient visits for ILI above their region-specific baseline levels.
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 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 47, the following ILI activity levels were experienced:
- Five states experienced high ILI activity (Alabama, Louisiana, Mississippi, Tennessee, and Texas).
- Two states experienced moderate ILI activity (Georgia and Missouri).
- Four states experienced low ILI activity (Hawaii, Ohio, Utah, and Virginia).
- New York City and 39 states experienced minimal ILI activity (Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Vermont, Washington, West Virginia, Wisconsin and Wyoming).
- Data were insufficient to calculate an ILI activity level from the District of Columbia.
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 47, the following influenza activity was reported:
- Widespread influenza activity was reported by 4 states (Alaska, Mississippi, New York, and South Carolina).
- Regional influenza activity was reported by 7 states (Alabama, Idaho, Iowa, Maine, Massachusetts, North Carolina, and Ohio).
- Local influenza activity was reported by 19 states (Arkansas, Colorado, Connecticut, Georgia, Illinois, Kansas, Kentucky, Louisiana, Minnesota, Missouri, Oregon, Rhode Island, South Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin and Wyoming).
- Sporadic influenza activity was reported by the District of Columbia, and 18 states (Arizona, California, Florida, Hawaii, Indiana, Maryland, Michigan, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, North Dakota, Oklahoma, Pennsylvania, Washington, and West Virginia).
- No influenza activity was reported by Guam and 1 state (Vermont).
- Puerto Rico, the U.S. Virgin Islands, and 1 state (Delaware) did not report.