- 263 (6.4%) 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 were positive for influenza.
- Over 99% of all subtyped influenza A viruses reported to CDC were 2009 influenza A (H1N1) viruses.
- The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
- One influenza-associated pediatric death was reported and was associated with an influenza B virus infection. This death occurred during the 2008-09 influenza season.
- The proportion of outpatient visits for influenza-like illness (ILI) was 1.7% which is below the national baseline of 2.3%. Two of 10 regions (Regions 4 and 9) reported ILI above region-specific baseline levels.
- No states reported widespread influenza activity, four states reported regional influenza activity, Puerto Rico and eight states reported local influenza activity, the District of Columbia, Guam, and 34 states reported sporadic influenza activity, four states reported no influenza activity, and the U.S. Virgin Islands did not report.
Antiviral Resistance Testing Results on Samples Collected Since September 1, 2009.
| Samples tested (n) | Resistant Viruses, Number (%) | Samples tested (n) | Resistant Viruses, Number (%) | Samples Tested (n) | Number (%) | |
| Oseltamivir | Zanamivir | Adamantanes | ||||
| Seasonal Influenza A (H1N1) | 1 | 1 (100.0) | 0 | 0 (0) | 1 | 0 |
| Influenza A (H3N2) | 12 | 0 (0) | 0 | 0 (0) | 12 | 12 (100.0) |
| Influenza B | 11 | 0 (0) | 0 | 0 (0) | N/A* | N/A* |
| 2009 Influenza A (H1N1) | 3881 | 48**^ (1.2) | 1429 | 0 (0) | 1458 | 1454 (99.7) |
*The adamantanes (amantadine and rimantadine) are not effective against influenza B viruses.
**Two screening tools were used to determine oseltamivir resistance: sequence analysis of viral genes or a neuraminidase inhibition assay.
^Additional laboratories perform antiviral resistance testing and report their results to CDC. Three additional oseltamivir resistant 2009 influenza A (H1N1) viruses have been identified by these laboratories since September 1, 2009, bringing the total number to 51.
CDC.FLUVIEW A Weekly Influenza Surveillance Report Prepared by the Influenza Division. Available at: http://www.cdc.gov/flu/weekly/.
Confirmed/Probable H1N1 Cases by US County