It\'s too soon to tell which flu strain will predominate this flu season but officials say strains chosen for the flu shot seem to resemble flu in South America. Officials at the Centers for Disease Control and Prevention in Atlanta say the United States experienced low levels of influenza activity from May 22 to Sept. 3, but influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses were detected worldwide and identified sporadically in the United States. \"Typical seasonal patterns of influenza activity occurred in the Southern Hemisphere,\" the report says. \"Although neither the influenza strain that will dominate nor the severity of influenza for the 2011/2012 U.S. influenza season can be predicted, antigenic characterization of viral isolates -- isolated virus strains -- during the summer appear antigenically similar to the influenza vaccine strains in the Northern Hemisphere 2011/2012 vaccine.\" To prevent influenza and its associated complications, influenza vaccination is recommended in all persons age 6 months and older, and should proceed for everyone without contraindications to vaccination as soon as vaccine is available in their community.