During week 45 (November 8-14, 2009) of the 2009-2010 influenza season, influenza activity decreased slightly in the U.S., according to the Centers for Disease Control and Prevention (CDC).

3,106 (28.8%) 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 being 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 for the seventh consecutive week.

Twenty-one influenza-associated pediatric deaths were reported. Fifteen of these deaths were associated with 2009 influenza A (H1N1) virus infection, and six were associated with an influenza A virus for which the subtype was undetermined.

The proportion of outpatient visits for influenza-like illness (ILI) was 5.5% which is above the national baseline of 2.3%. All 10 regions reported ILI above region-specific baseline levels.

Forty-three states reported geographically widespread influenza activity, Puerto Rico and seven states reported regional influenza activity, the District of Columbia reported local influenza activity, and Guam and the U.S. Virgin Islands reported sporadic influenza activity.

From August 30 – November 14, 2009, 26,315 laboratory-confirmed influenza-associated hospitalizations and 1,049 laboratory-confirmed influenza-associated deaths were reported to CDC.

During week 45, the following influenza activity was reported:

Widespread influenza activity was reported by 43 states (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, and Wisconsin).

Regional influenza activity was reported by Puerto Rico and seven states (Hawaii, Mississippi, Nebraska, North Dakota, South Carolina, Texas, and Wyoming).

Local influenza activity was reported by the District of Columbia.

Sporadic influenza activity was reported by the U.S. Virgin Islands and Guam.