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.