There was a sharp spike in influenza for the week of Nov. 18 especially in the Southeast and parts of the Midwest, U.S. officials said.
A report by the Centers for Disease Control and Prevention in Atlanta said of 5,342 specimens tested, 15.2 percent were positive for influenza.
Five states experienced high influenza-like illness activity -- Illinois, Indiana, Michigan, Ohio and Wisconsin -- two states experienced moderate influenza-like illness activity and four states experienced low influenza-like illness activity. New York City and 39 states experienced minimal -- hardly any -- influenza-like illness activity and the District of Columbia had insufficient data.
Flu vaccines are designed to protect against three influenza viruses that influenza experts predict will be the most common during the upcoming season. Three kinds of influenza viruses commonly circulate among people: influenza B viruses, influenza A (H1N1) viruses, and influenza A (H3N2) viruses. Each year, one flu virus of each kind is used to produce seasonal influenza vaccine.
The 2012-2013 influenza vaccine is made from the following three viruses:
-- An A/California/7/2009 (H1N1)pdm09-like virus.
-- An A/Victoria/361/2011 (H3N2)-like virus.
-- A B/Wisconsin/1/2010-like virus from the B/Yamagata lineage of viruses.
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