What is the most common cause of gastroenteritis (inflammation of the stomach and intestines) in the United States?

Norovirus is the Leading Cause of Gastroenteritis in the United States

Norovirus is definitively the #1 cause of gastroenteritis in the United States, accounting for approximately 21 million illnesses annually and representing the leading cause of acute gastroenteritis across all age groups in both community and healthcare settings. 1

Epidemiologic Evidence

Overall Disease Burden

• Norovirus causes an estimated 21 million illnesses per year in the United States, making it the most common cause of gastroenteritis across all age groups 1
• Among all gastroenteritis pathogens assessed by CDC's FoodNet surveillance, norovirus accounts for 58% of gastroenteritis illnesses overall, far exceeding other pathogens 2
• Norovirus is responsible for one in 15 U.S. residents becoming ill each year, along with 56,000-71,000 hospitalizations and 570-800 deaths 3

Sporadic Disease Patterns

• Recent studies demonstrate that norovirus is the leading cause of acute gastroenteritis in the community and among persons seeking care in outpatient clinics or emergency departments across all age groups 1
• Systematic reviews estimate that noroviruses account for 10%-15% of severe gastroenteritis cases in children aged <5 years and 9%-15% of mild and moderate diarrhea cases among persons of all ages 1
• In the post-rotavirus vaccine era, norovirus has replaced rotavirus as the leading cause of acute gastroenteritis in vaccinated children, causing nearly 1 million ambulatory care visits and 14,000 hospitalizations annually 2

Outbreak Predominance

National Outbreak Data

• Norovirus is the predominant cause of gastroenteritis outbreaks worldwide, responsible for approximately 50% of all reported gastroenteritis outbreaks (range: 36%-59%) in the United States and European countries 1
• During 2009-2013, of 7,430 AGE outbreaks with a suspected or confirmed etiology, norovirus was reported in 6,223 (84%) of these outbreaks 4
• Among foodborne disease outbreaks specifically, norovirus constitutes 48% of all foodborne outbreaks with a single known cause during 2009-2012 3

Transmission Routes

• The majority of norovirus outbreaks involve person-to-person transmission, though foodborne transmission accounts for approximately one quarter of the 21 million annual illnesses 1
• Of 520 outbreaks with contributing factors reported, food workers were implicated as the contamination source in 70% 3
• Restaurants are the most common setting (64%) of food preparation in norovirus outbreaks 3

Comparison to Other Pathogens

Rotavirus Context

• While rotavirus historically was a major cause of gastroenteritis, widespread rotavirus vaccination has dramatically reduced its burden 2
• In the prevaccine era, rotavirus accounted for 30%-50% of hospitalizations for gastroenteritis among U.S. children aged <5 years, but this has been substantially reduced through vaccination programs 1
• Rotavirus vaccines prevent most severe disease, with documented effectiveness in reducing rotavirus disease by two-thirds 2

Other Viral Pathogens

• Caliciviruses, astroviruses, and adenoviruses account for much smaller proportions of gastroenteritis cases compared to norovirus 1
• These other viral pathogens primarily affect specific age groups (children or elderly) in institutional settings, whereas norovirus affects all ages across diverse settings 1

Clinical and Public Health Implications

Disease Characteristics

• Norovirus infections are highly contagious, requiring as few as 10 viral particles to cause infection 2
• The virus demonstrates remarkable environmental stability and can remain infective even if frozen for years or heated to 60°C for 30 minutes 1
• Peak viral shedding occurs 2-5 days after infection, with viral shedding continuing for an average of 4 weeks following infection 5

Prevention Priorities

• Hand hygiene with soap and running water for a minimum of 20 seconds is the most effective method to reduce norovirus contamination 5
• Ill healthcare workers, food handlers, and childcare workers should be excluded from work until 48-72 hours after symptom resolution 5
• Environmental disinfection and isolation of ill persons are critical control measures in institutional settings 4