Influenza levels in the US are the highest they've been in 15 years amid winter weather and a second wave of the virus.

The winter flu season features two types of influenza. Here's what you need to know about them and how they differ.

The U.S. winter virus season is in full force, and by one measure is the most intense in 15 years.

Flu infections are at or near their highest levels in at least 15 years and are still rising, the Centers for Disease Control and Prevention says.

More than 24 million people have had seasonal flu this season, according to estimates from the Centers for Disease Control ...

Nasal sprays can provide relief from flu symptoms by reducing nasal congestion and inflammation, making it easier to breathe.

CNN’s Dr. Sanjay Gupta discusses the severity of the flu season in the US and how people can protect themselves.