Flu season is back, and this year's strain of the virus is especially brutal. People are flocking to hospitals across the country with debilitating flu-like symptoms, and some deaths related to complications of the flu have already been reported.
The flu outbreak is so severe in Boston that Mayor Thomas Menino declared a health emergency this week, setting off alarm bells in New England and beyond. But why is the 2013 influenza strain so bad? Dr. Joseph Bresee, chief of the Epidemiology and Prevention Branch at the Center for Disease Control's Influenza Division, explains.