The flu has infected "significantly" more Americans this winter than usual, says a doctor and infectious disease specialist.

Flu season in the U.S. is particularly bad this year, and a new branch of the flu family tree may be to blame.

When the flu comes at you, brace yourself for a tough time. “It’s like a truck hit you,” says Carlene Muto, MD, an infectious disease specialist and medical director of infection prevention at Temple ...