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Most States Have Widespread Flu Outbreaks, Young and Middle-aged at Greatest Risk


All regions of the U.S. are now experiencing influenza outbreaks, predominantly with the H1N1 "swine flu" strain, according to the Centers for Disease Control and Prevention (CDC). In contrast to some prior flu epidemics, young and middle-aged adults -- rather than young children and elderly people -- appear to have the highest risk of serious complications and death.

The CDC's latest "FluView" covers the first week of the official flu season, which ended on January 4. During this period, 2486 confirmed influenza cases were identified by U.S. laboratories that collaborate with the World Health Organization and National Respiratory and Enteric Virus Surveillance System. Almost all (97%) were due to influenza A, with the most common strain (57%) being the H1N1 variant that caused a global pandemic in 2009.


The number of flu cases has risen sharply in recent weeks, with the proportion of medical visits attributable to flu-like illness more than doubling to 4.4%. 35 states (Alabama, Alaska, Arkansas, California, Colorado, Connecticut, Georgia, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Texas, Utah, Virginia, Washington, Wisconsin, and Wyoming) have reported widespread influenza outbreaks. 20 states -- concentrated in the southern Midwest -- experienced high influenza-like illness activity and 7 had moderate activity, while 11 had low and 12 had minimal activity.

So far there have been 2622 confirmed influenza-associated hospitalizations, or 9.7 per 100,000 people, with about 60% occurring among people between the ages of 18 and 64 -- a group that is less likely to receive the flu vaccine. However, the CDC noted that the proportion of all deaths attributed to influenza and pneumonia during the period "was below the epidemic threshold" of 7.1%.

The CDC continues to recommend that everyone receive the flu vaccine, which includes the predominant 2009 H1N1 strain along with 3 other variants. The recommendation is especially strong for children, older adults, women who are or plan to become pregnant during flu season, heath-care providers and child-care workers, and people with immune suppression -- including people with HIV -- and certain other disease. Both an injected killed virus vaccine and a nasal attenuated virus version are available, but the latter should not be used by children younger than 2 years, people older than 49 years, pregnant women, or people with immune deficiency.



Centers for Disease Control and Prevention. 2013-2014 Influenza Season Week 1 ending January 4, 2014. CDC FluView. January 10, 2014.