Your Questions About Norovirus, Answered

Norovirus is a highly contagious RNA virus and the most common cause of acute gastroenteritis — illness characterized by nausea, vomiting, diarrhea, and stomach cramping — in people of all ages worldwide. The virus belongs to the family Caliciviridae and includes multiple genetically distinct genogroups, of which GII.4 is responsible for the majority of global outbreaks.

According to the CDC, norovirus causes approximately 21 million illnesses, 109,000 hospitalizations, and 900 deaths in the United States each year. Globally, it accounts for roughly 685 million cases and 200,000 deaths annually, disproportionately affecting children under five and elderly adults in low-income settings.

The virus is extraordinarily infectious. As few as 18 viral particles are sufficient to cause infection — an almost undetectably small dose. Norovirus survives on surfaces for days and resists many common disinfectants, making it a persistent challenge in healthcare facilities, schools, cruise ships, and food-service environments.

There is no approved vaccine and no specific antiviral treatment as of 2026. Management is primarily supportive: oral rehydration to prevent dehydration, rest, and strict hygiene to prevent spread.