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CDC FluView Wk 5: H1N1 Edges Out H3N2

 

 


# 5307

 

 

After several months where seasonal H3N2 has pretty much dominated the U.S. flu season, the latest FluView report from the CDC shows that the 2009 H1N1 virus has – by a narrow margin – finally edged out the competition.

 

Of positive flu samples subtyped, 28.5% were H1N1 while 28.3% were H3N2.

 

Overall, influenza activity in week 5 continued to climb, with 19 states reporting high influenza-like activity.

 

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Week 5 also saw a marked increase in pediatric flu-related fatalities (11), and for the second week in a row the P&I mortality rate was at or above the epidemic level.

 

A few excerpts from this week’s report follows:

 

 

2010-2011 Influenza Season Week 5 ending February 5, 2011

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

Synopsis:

During week 5 (January 30-February 5, 2011), influenza activity in the United States increased.

  • Of the 7,511 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, 2,377 (31.7%) were positive for influenza.
  • The proportion of deaths attributed to pneumonia and influenza (P&I) was at the epidemic threshold.
  • Eleven influenza-associated pediatric deaths were reported. Four of these deaths were associated with influenza B viruses, two of these deaths were associated with 2009 influenza A (H1N1) virus, one was associated with an influenza A (H3) virus, and four were associated with an influenza A virus for which the subtype was not determined.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 4.6%, which is above the national baseline of 2.5%. Nine of the 10 regions (Regions 1, 2, 3, 4, 5, 6, 7, 8, and 10) reported ILI at or above region-specific baseline levels. Nineteen states experienced high ILI activity; nine states experienced moderate ILI activity; New York City and 10 states experienced low ILI activity; 12 states experienced minimal ILI activity, and the District of Columbia had insufficient data.
  • The geographic spread of influenza in 37 states was reported as widespread; nine states reported regional influenza activity; the District of Columbia reported local activity, and Guam, Puerto Rico, the U.S. Virgin Islands, and four states reported sporadic influenza activity.

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Pneumonia and Influenza (P&I) Mortality Surveillance

During week 5, 8.0% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was at the epidemic threshold of 8.0% for week 5.

Pneumonia And Influenza Mortality

Influenza-Associated Pediatric Mortality

Eleven influenza-associated pediatric deaths were reported to CDC during week 5. Four of these deaths were associated with influenza B viruses, two of these deaths were associated with 2009 influenza A (H1N1) virus, one was associated with an influenza A (H3) virus, and four were associated with an influenza A virus for which the subtype was not determined. Thirty deaths from 18 states (Arizona, Colorado, Florida, Georgia, Illinois, Indiana, Louisiana, Michigan, New Jersey, New York, North Carolina, North Dakota, Oklahoma, Pennsylvania, Texas, Utah, Virginia, and West Virginia) and New York City have been reported during this influenza season.

 

Twelve of the 30 deaths reported were associated with influenza B viruses, nine deaths reported were associated with influenza A (H3) viruses, three were associated with 2009 influenza A (H1N1) viruses, and six were associated with an influenza A virus for which the subtype was not determined.

Influenza-Associated Pediatric Mortality

Outpatient Illness Surveillance:

Nationwide during week 5, 4.6% 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 above the national baseline of 2.5%.

national levels of ILI and ARI

Related Post:

CDC
FluView
Influenza Activity

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