Stomach flu cases are on the rise in the Washington metropolitan area and across the United States as cold weather and the holiday season push more people indoors.

Nationwide, the Centers for Disease Control and Prevention reported 91 outbreaks of norovirus, the formal name for the stomach bug, during the week of Dec. 5, 2024. That is up from 69 outbreaks over the Thanksgiving holiday and 32 outbreaks the week of Nov. 21, 2024.