2011-2012 Influenza Season Week 47 ending November 26, 2011
All data are preliminary and may change as more reports are received.
Synopsis:
National and Regional Summary of Select Surveillance Components
| HHS Surveillance Regions* |
Data for current week |
Data cumulative since October 2, 2011 (Week 40) |
| Out-patient ILI† |
% of respiratory specimens positive for flu‡ |
Number of jurisdictions reporting regional or widespread activity§ |
A (H3) |
2009 A (H1N1) |
A(Subtyping not performed) |
B |
Pediatric Deaths |
| Nation |
Normal |
1.9% |
0 of 54 |
79 |
8 |
104 |
75 |
0 |
| Region 1 |
Normal |
0.0% |
0 of 6 |
1 |
0 |
0 |
3 |
0 |
| Region 2 |
Normal |
0.4% |
0 of 4 |
2 |
0 |
2 |
1 |
0 |
| Region 3 |
Normal |
0.3% |
0 of 6 |
2 |
0 |
3 |
0 |
0 |
| Region 4 |
Normal |
3.4% |
0 of 8 |
8 |
1 |
74 |
48 |
0 |
| Region 5 |
Normal |
1.5% |
0 of 6 |
10 |
2 |
1 |
6 |
0 |
| Region 6 |
Normal |
0.3% |
0 of 5 |
4 |
0 |
2 |
8 |
0 |
| Region 7 |
Normal |
0.9% |
0 of 4 |
6 |
0 |
3 |
1 |
0 |
| Region 8 |
Normal |
2.3% |
0 of 6 |
20 |
1 |
11 |
0 |
0 |
| Region 9 |
Normal |
0.5% |
0 of 5 |
18 |
4 |
4 |
6 |
0 |
| Region 10 |
Normal |
0.7% |
0 of 4 |
8 |
0 |
4 |
2 |
0 |
WHO and NREVSS collaborating laboratories located in all 50 states 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 47 |
| No. of specimens tested |
2,130 |
| No. of positive specimens (%) |
40 (1.9%) |
| Positive specimens by type/subtype |
|
| Influenza A |
33 (82.5%) |
| A (2009 H1N1) |
1 (3.0%) |
| A (subtyping not performed) |
26 (78.8%) |
| A (H3) |
6 (18.2%) |
| Influenza B |
7 (17.5%) |
View National and Regional Level Graphs and Data | View Chart Data | View Full Screen | View PowerPoint Presentation 
Antigenic Characterization:
CDC has antigenically characterized 21 influenza viruses [one 2009 influenza A (H1N1), 16 influenza A (H3N2) viruses, and four influenza B viruses] collected by U.S. laboratories since October 1, 2011.
Influenza A (H1N1) [1]
- One virus was characterized as A/California/7/2009-like, the influenza A (H1N1) component of the 2011-12 influenza vaccine for the Northern Hemisphere.
Influenza A (H3N2) [16]
- All 16 were characterized as A/Perth/16/2009-like, the influenza A (H3N2) component of the 2011-12 influenza vaccine for the Northern Hemisphere.
Influenza B (B/Victoria/02/87 and B/Yamagata/16/88 lineages) [4]:
- Victoria Lineage [3]: Three of four B viruses tested belong to the B/Victoria lineage of viruses and were characterized as B/Brisbane/60/2008-like, the recommended influenza B component for the 2011-12 Northern Hemisphere influenza vaccine.
- Yamagata Lineage [1]: One of four B viruses tested belongs to the B/Yamagata lineage of viruses.
It is too early in the influenza season to determine how well the seasonal vaccine and circulating strains will match.
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 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, 2011
|
Oseltamivir |
Zanamivir |
| Virus Samples tested (n) |
Resistant Viruses, Number (%) |
Virus Samples tested (n) |
Resistant Viruses, Number (%) |
| Influenza A (H3N2) |
24 |
0 (0.0) |
24 |
0 (0.0) |
| Influenza B |
2 |
0 (0.0) |
2 |
0 (0.0) |
| Influenza A (2009 H1N1) |
5 |
0 (0.0) |
5 |
0 (0.0) |
All viruses tested for the 2011-2012 season since October 1, 2011 have been susceptible to the neuraminidase inhibitor antiviral medications oseltamivir and zanamivir as were the majority of viruses tested last season; 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).
During week 47, 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 7.1% for week 47.
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Two influenza-associated pediatric deaths were reported to CDC during week 47. One death was associated with an influenza A (H3) virus and one was associated with a 2009 H1N1 virus. These deaths occurred during the 2010-11 influenza season and bring the total number of reported pediatric deaths occurring during that season to 120. No influenza-associated pediatric deaths occurring during the 2011-12 season have been reported to CDC.
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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.
Nationwide during week 47, 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 2.4%. (ILI is defined as fever (temperature of 100°F [37.8°C] or greater) and cough and/or sore throat.)
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 2.1% during week 47. 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 47, the following ILI activity levels were experienced:
- All 50 states and New York City experienced minimal ILI activity (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, 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, and Wyoming).
- Data were insufficient to calculate an ILI activity level from the District of Columbia.
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The influenza activity reported by state and territorial epidemiologists indicates geographic spread of influenza viruses, but does not measure the intensity of influenza activity.
During week 47, the following influenza activity was reported:
- Local influenza activity was reported by one state (Massachusetts).
- Sporadic influenza activity was reported by the District of Columbia, Guam, and 29 states (Alaska, Arkansas, California, Colorado, Connecticut, Florida, Hawaii, Illinois, Indiana, Iowa, Kentucky, Louisiana, Minnesota, Mississippi, Nebraska, Nevada, New Mexico, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Carolina, Texas, Utah, Washington, West Virginia, and Wisconsin).
- No influenza activity was reported by the U.S. Virgin Islands and 21 states (Alabama, Arizona, Delaware, Georgia, Idaho, Kansas, Maine, Maryland, Michigan, Missouri, Montana, New Hampshire, New Jersey, North Carolina, Oklahoma, Oregon, South Dakota, Tennessee, Vermont, Virginia, and Wyoming).
- Puerto Rico did not report.
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