- 119 (3.2%) 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.
- 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 above the epidemic threshold.
- Nine influenza-associated pediatric deaths were reported. Eight deaths were associated with 2009 influenza A (H1N1) virus infection and one was associated with an influenza A virus for which the subtype was undetermined.
- The proportion of outpatient visits for influenza-like illness (ILI) was 1.9% which is below the national baseline of 2.3%. All regions reported ILI below their region-specific baseline.
- No states reported widespread influenza activity, six states reported regional influenza activity, Puerto Rico and 10 states reported local influenza activity, the District of Columbia, Guam, and 31 states reported sporadic influenza activity, and the U.S. Virgin Islands and three states reported no influenza activity.
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) | 11 | 0 (0) | 0 | 0 (0) | 10 | 11 (100.0) |
| Influenza B | 7 | 0 (0) | 0 | 0 (0) | N/A* | N/A* |
| 2009 Influenza A (H1N1) | 3329 | 46**^ (1.4) | 1077 | 0 (0) | 1098 | 1095 (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 49.
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