2013-2014 Influenza Season Week 41 ending October 12, 2013

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

This FluView is in the abbreviated format due to the partial government shut-down from October 1-16, 2013.

Synopsis:

During week 41 (October 6-12, 2013), influenza activity remained low in the United States.

• Viral Surveillance: Of 3,534 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 41, 166 (4.7%) 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 1.1%, below the national baseline of 2.0%. All 10 regions reported ILI below region-specific baseline levels. Two states experienced low ILI activity, 48 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 Puerto Rico was reported as regional; 3 states reported local influenza activity; Guam, the District of Columbia, the U.S. Virgin Islands, and 24 states reported sporadic influenza activity; 22 states reported no influenza activity, and one state did not report.

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

*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 http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.

	Week 41
No. of specimens tested	3,534
No. of positive specimens (%)	166 (4.7%)
Positive specimens by type/subtype
Influenza A	151 (91.0%)
2009 H1N1	38 (25.2%)
Subtyping not performed	104 (68.9%)
H3	9 (6.0%)
Influenza B	15 (9.0%)

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

Novel Influenza A Virus

One infection with an influenza A (H3N2) variant virus (H3N2v) was reported to CDC by Iowa. Contact between the case patient and swine in the week preceding illness was reported. The patient has fully recovered and no further cases have been identified in contacts of the case patient. This is the first H3N2v infection reported for the 2013-2014 influenza season, which began on September 29, 2013.

Additional information on influenza in swine, variant influenza infection in humans, and strategies to interact safely with swine can be found at http://www.cdc.gov/flu/swineflu/h3n2v-cases.htm

Pneumonia and Influenza (P&I) Mortality Surveillance

During week 41, 5.6% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.1% for week 41.

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Influenza-Associated Pediatric Mortality

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

Additional data can be found at http://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html.

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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: http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html and http://gis.cdc.gov/grasp/fluview/FluHospChars.html.

Outpatient Illness Surveillance

Nationwide during week 41, 1.1% 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 2.0%. (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.

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 2.5% during week 41. All 10 regions reported a proportion of outpatient visits for ILI below 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 41, the following ILI activity levels were experienced:

• Two states experienced low ILI activity (Texas and Vermont).
• Forty-eight 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, Utah, Virginia, Washington, West Virginia, Wisconsin, and Wyoming).
• Data were insufficient to calculate an ILI activity level from the District of Columbia.

 

*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:

• Regional influenza activity was reported by Puerto Rico.
• Local influenza activity was reported by three states (Alabama, South Carolina and Texas).
• Sporadic influenza activity was reported by the District of Columbia, Guam, the U.S. Virgin Islands, and 24 states (Alaska, Arizona, California, Connecticut, Florida, Georgia, Hawaii, Indiana, Iowa, Louisiana, Maryland, Massachusetts, Minnesota, Mississippi, New Jersey, New Mexico, New York, North Dakota, Ohio, South Dakota, Utah, Washington, Wisconsin, and Wyoming).
• No influenza activity was reported by 22 states (Arkansas, Colorado, Delaware, Idaho, Illinois, Kansas, Kentucky, Maine, Michigan, Missouri, Montana, Nebraska, New Hampshire, North Carolina, Oklahoma, Oregon, Pennsylvania, Rhode Island, Tennessee, Vermont, Virginia, and West Virginia).
• One state (Nevada) did not report.