"The flu" has several strains, with flu A and flu B considered the most common and most severe. Here's what to know as flu ...

This flu season medics have been struck by the uptick of cases involving the type B flu virus, which has been predominating the season for the first time in 27 years. Influenza can be split into four ...

The mutation, known as subclade K, has already caused a surge in flu cases in Australia, Canada, Japan, and the U.K.

Researchers are striving to understand the impact a phenomenon known as original antigenic sin has on immunity to the virus.

Flu season is starting to tick up in the U.S. And, looking at clues from other countries, we may be in for a rough winter. But not all influenza is the same. And there are some notable differences ...