2011-2012 Influenza Season Week 31 ending August 4, 2012

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

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. Region specific data can be found at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.

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Novel Influenza A Virus:

From July 12 through August 9, 2012, a total of 153 infections with influenza A (H3N2) variant (H3N2v) viruses have been reported in four states (Hawaii [1], Illinois [1], Indiana [120], and Ohio [31]). So far during the current outbreaks, two persons have been hospitalized as a result of their illness; no deaths have occurred. At this time no ongoing human-to-human transmission has been identified and all cases have reported contact with swine prior to illness onset. Public health and agriculture officials are investigating the extent of disease among humans and swine, and additional cases are likely to be identified as the investigation continues. Additional information on these cases can be found in the MMWR. Because of reporting deadlines, the state totals reported by CDC may not always be consistent with those reported by state health departments. If there is a discrepancy between these two counts, data from the state health departments should be used as the most accurate number.

CDC is required to report all cases of human infection with novel (non-human) influenza viruses – including influenza viruses of swine origin – to the World Health Organization (WHO) as part of the International Health Regulations (IHR). Domestically, CDC reports these cases in this report and on its website. Early identification and investigation of human infections with novel influenza A viruses is critical in order to evaluate the extent of the outbreak and possible human-to-human transmission. Additional information on influenza in swine, variant influenza infection in humans, and strategies to interact safely with livestock can be found at http://www.cdc.gov/flu/swineflu/influenza-variant-viruses-h3n2v.htm.

Pneumonia and Influenza (P&I) Mortality Surveillance:

During week 31, 5.8% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.5% for week 31.

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Influenza-Associated Pediatric Mortality:

No influenza-associated pediatric deaths were reported to CDC during week 31. A total of 34 influenza-associated pediatric deaths have been reported during the 2011-2012 season. 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. Additional FluSurv-NET data can be found at: http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html.

Outpatient Illness Surveillance:

Nationwide during week 31, 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 2.4%. (ILI is defined as fever (temperature of 100°F [37.8°C] or greater) and cough and/or sore throat.) Region specific data can be found at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.

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Additional National and International Influenza Surveillance Information

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 FluNet and the Global Epidemiology Reports

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