Abstract Title
Oyster-associated norovirus outbreaks in the United States, January 2009—December 2024
Presenter
Anita K. Kambhampati, Centers for Disease Control and Prevention
Co-Author(s)
Mary E. Wikswo1, Preethi Sundararaman2, Sara A. Mirza1. 1Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. 2Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
Abstract Category
Epidemology
Abstract
Background: Oysters, which are commonly eaten raw, are often implicated in foodborne norovirus outbreaks. Oysters can become contaminated with norovirus in harvest waters or during preparation and transmit norovirus to humans when eaten.
Methods: The National Outbreak Reporting System (NORS) collects reports of foodborne, waterborne, and enteric disease outbreaks in the United States. We analyzed data on norovirus outbreaks occurring January 1, 2009–December 31, 2024, with oysters as the sole implicated food; 2024 data are preliminary. Our analysis included confirmed (≥2 laboratory-confirmed case-patients) and suspected (<2 laboratory-confirmed case-patients) norovirus outbreaks.
Results: During January 2009–December 2024, 98 oyster-associated norovirus outbreaks were reported, with an annual median of 5 outbreaks (range: 1–20). In total, 2,084 primary case-patients were reported, with a median of 6 case-patients (range: 2–361) per outbreak. Among primary case-patients with information, 105/1,216 (9%) sought medical care, 42/1,336 (3%) visited an emergency department, and 19/1,687 (1%) were hospitalized; no deaths were reported. Eighty-nine (91%) outbreaks were associated with oyster consumption in a single state; 9 (9%) were associated with oysters consumed in multiple states. Multistate outbreaks were generally larger (median: 55 case-patients, range: 16–361) compared with single state outbreaks (median: 5 case-patients, range: 2–87).
Conclusions: Oyster-associated norovirus outbreaks remain a public health risk in the United States. Oysters should be cooked thoroughly to an internal temperature of at least 145°F before consumption. Prompt investigation, management, and reporting of oyster-associated norovirus outbreaks is crucial to prevent further illness.
Methods: The National Outbreak Reporting System (NORS) collects reports of foodborne, waterborne, and enteric disease outbreaks in the United States. We analyzed data on norovirus outbreaks occurring January 1, 2009–December 31, 2024, with oysters as the sole implicated food; 2024 data are preliminary. Our analysis included confirmed (≥2 laboratory-confirmed case-patients) and suspected (<2 laboratory-confirmed case-patients) norovirus outbreaks.
Results: During January 2009–December 2024, 98 oyster-associated norovirus outbreaks were reported, with an annual median of 5 outbreaks (range: 1–20). In total, 2,084 primary case-patients were reported, with a median of 6 case-patients (range: 2–361) per outbreak. Among primary case-patients with information, 105/1,216 (9%) sought medical care, 42/1,336 (3%) visited an emergency department, and 19/1,687 (1%) were hospitalized; no deaths were reported. Eighty-nine (91%) outbreaks were associated with oyster consumption in a single state; 9 (9%) were associated with oysters consumed in multiple states. Multistate outbreaks were generally larger (median: 55 case-patients, range: 16–361) compared with single state outbreaks (median: 5 case-patients, range: 2–87).
Conclusions: Oyster-associated norovirus outbreaks remain a public health risk in the United States. Oysters should be cooked thoroughly to an internal temperature of at least 145°F before consumption. Prompt investigation, management, and reporting of oyster-associated norovirus outbreaks is crucial to prevent further illness.