This weeks influenza report from the CDC for the 2012-2013 influenza season, week 50 ending Dec. 15, 2012 shows continued increases in flu activity in the United States. The CDC says its still too early to tell how severe the season might be. Most of the U.S. flu viruses analyzed by the CDC this season are well matched to the viruses in this season's vaccine. Flu is unpredictable and it's not known how long the season will last, but significant activity has been observed previously as late as May.
"Todays report confirms that the U.S. flu season is off to early start, says CDC director Dr. Thomas Frieden. Its too early to tell how severe our season might be. However, we know that thousands die and hundreds of thousands of people are hospitalized with flu each year. Vaccination is the single most important step we can take to protect ourselves and our families against infection. It's not too late to get vaccinated before the flu season peaks.
 During week 50 (Dec. 9-15, 2012), influenza activity increased in the U.S.
- Viral Surveillance: Of 9,562 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System\ (NREVSS) collaborating laboratories in week 50, 2,709 (28.3 percent) were positive for influenza.
- Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
- Influenza-Associated Pediatric Deaths: Two influenza-associated pediatric deaths were reported. One was associated with an influenza A (H3) virus and one was associated with an influenza A virus for which the subtype was not determined.
- Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 3.2 percent; above the national baseline of 2.2 percent. Nine of 10 regions reported ILI above region-specific baseline levels. Twelve states experienced high ILI activity, New York City and five states experienced moderate ILI activity; 11 states experienced low ILI activity; 22 states experienced minimal ILI activity, and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: Twenty-nine states reported widespread geographic
influenza activity; 12 states reported regional activity; the District of Columbia and five states reported local activity; three states reported sporadic activity; Guam reported no influenza activity, and Puerto Rico, the U.S. Virgin Islands, and one state did not report.
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