'MURICA — The flu has arrived early in North America, as officials worry this season's outbreak could be severe. <br /> <br />According to the Center for Disease Control and Prevention (CDC), the percentage of patients reporting flu-like symptoms reached the 2.2 percent threshold by late November, indicating flu season had begun, USA Today reported. <br /> <br />Experts believe the U.S. could be hit hard by the H3N2 strain, the same strain behind Australia's especially bad flu season. <br /> <br />The flu vaccine has been shown to be 10 percent against H3N2, according to a research paper in Eurosurveillance. <br /> <br />Flu vaccines cause antibodies to develop in the body around two weeks after vaccination, according the the CDC. <br /> <br />These antibodies then help the body fight against virus infections that are in the vaccine. <br />The seasonal flu vaccine is designed to protect against influenza viruses researchers predict will be the most common during the upcoming season, the CDC reported.
