Norovirus, a gross stomach bug, appears to be hitting NYC. Good luck finding out where.

Stomach illness is rising in New York City. The number of New Yorkers visiting hospital emergency rooms due to vomiting or diarrhea has risen about 50% from December to mid-February, according to the city health department’s EpiQuery data portal.

The most likely culprit is norovirus, a common intestinal germ that spreads easily through food and person-to-person contact. But city, state and federal officials can’t say for sure.

Health experts said that’s because norovirus is poorly tracked, even though it’s estimated to cause billions of dollars in annual economic losses nationally due to missed work and school.

Health reporter Betsy Ladyzhets joined WNYC's Sean Carlson to share her reporting on the subject.