CDC: Flu season past its peak but still going strong

ATLANTA — According to the Centers for Disease Control and Prevention's FluView report released Friday, flu activity remains high overall, but is declining in parts of the country while increasing in other parts of the country. Most notably the Southeast, which began experiencing high levels of flu activity at the end of November, is now showing declines in activity. 

Flu activity is likely to continue for some time, the agency projected. Anyone aged 6 months and older who has not gotten a flu vaccine yet this season should get one now, especially if they are in a part of the country where activity is still at a high level, CDC advised. 

For the week of Jan. 12 to 18, the proportion of people seeing their health care provider for influenza-like illness decreased for the third week, but remains above the national baseline. All ten regions continue to report ILI activity above their region-specific baseline level. ILI activity is increasing among some Western and Northeastern states. 

Thirteen states experienced high ILI activity. This is a decrease from the 14 states that reported high ILI activity last week. Seven states and New York City experienced moderate ILI activity. Fifteen states experienced low ILI activity. Fifteen states experienced minimal ILI activity. 

Forty-one states reported widespread geographic influenza activity; an increase from the 40 states that reported widespread activity in the previous week. Puerto Rico and eight states reported regional activity. The District of Columbia reported local activity and Guam and Hawaii reported sporadic influenza activity. The U.S. Virgin Islands reported no influenza activity.

The highest hospitalization rates are among people 65 and older and children younger than 5 years. This is typical of most flu seasons.

However, of the 4,615 influenza-associated hospitalizations that have been reported this season, 61% have been in people ages 18 to 64 years. More commonly, most flu hospitalizations occur in people 65 and older. This pattern of more hospitalizations among younger people was also seen during the 2009 H1N1 pandemic.

Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. To date, influenza A (H1N1) viruses have predominated. This is the H1N1 virus that emerged in 2009 to cause a pandemic and is the first season that the virus has circulated at such high levels since the pandemic. During the week of January 12-18, 2,707 of the 2,793 influenza-positive tests reported to CDC were influenza A viruses and 86 were influenza B viruses. Of the 1,785 influenza A viruses that were subtyped, 3.2% were H3 viruses and 96.8% were 2009 H1N1 viruses.

As many as 710 (99.8%) of the 711 2009 H1N1 viruses tested were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere quadrivalent and trivalent vaccines for the 2013-2014 season.