Norovirus, also known as the stomach bug, is spreading across the U.S. Here's what to know about the contagious virus and how best to prevent an infection.

The start of the new year hasn’t been too kind to millions of Americans, who have had their bellies bulldozed by the norovirus. Though previously uncommon, this particular strain, dubbed GII.17[P17],

A highly contagious strain of norovirus, GII.17, is rapidly spreading across the United States, fueling an unusually high number of outbreaks, according to the Centers for Disease Control and Prevention (CDC).

New CDC data indicates a rise in cases of norovirus, often colloquially referred to as "stomach flu." Test positivity has spiked.

This winter's wave of norovirus infections has reached levels that are now more than double last season's peak, in figures published Monday by the Centers for Disease Control and Prevention tracking the notorious stomach bug.

The latest wave of norovirus infections have more than doubled last season's peak, the CDC said. Almost 30% of norovirus tests taken the week of new year's were positive for the virus. Rates have reached or surpassed last season's peaks in all regions across the country.