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Understanding the Norovirus Current Outbreak Map: A Deep Dive into the 2024-2025 Surge
Estimated reading time: 8 minutes
- The 2024-2025 norovirus season saw a significant surge in outbreaks, reaching decade-high levels.
- Multiple surveillance systems track norovirus activity, though a single, real-time map isn’t publicly available.
- Regional variations in outbreak severity were observed, with some areas experiencing particularly high numbers of cases.
- Robust hygiene practices, employee training, and outbreak response plans are crucial for mitigation.
- Staying informed about regional activity through official sources is key for proactive risk assessment.
The 2024-2025 Norovirus Surge: A Decade-High
The 2024-2025 norovirus season showed a dramatic increase in reported outbreaks. Data from the U.S. Centers for Disease Control and Prevention (CDC) reveals a concerning trend. From August 1, 2024, to mid-January 2025, the CDC reported 1,078 norovirus outbreaks in the United States – nearly double the 557 outbreaks reported during the same period in 2023-2024. This upward trend continued, with 2,630 outbreaks reported by early July 2025, exceeding the 1,449 outbreaks reported in the corresponding period of the previous season. This surpasses the range observed in 2012-2020 and 2021-2024.
The increase wasn’t gradual; early December 2024 saw a sharp rise, with 91 outbreaks reported during the week of December 5th – a substantial increase from the 69 outbreaks the previous week. This exceeded the average maximum of 65 outbreaks for the same week over the preceding 12 years. This wasn’t limited to the U.S. England reported over 9,000 laboratory-confirmed norovirus cases by February 2025 – more than double their five-year seasonal average. Confirmed infections and hospital outbreaks were 50% to 60% higher than the recent average. Cruise ships saw nearly 900 people affected in December 2024 alone, contributing to 16 outbreaks – the highest in 12 years, with five occurring in December 2024.
Understanding Norovirus Surveillance and Reporting Systems
- National Outbreak Reporting System (NORS) and CaliciNet: NORS and CaliciNet collect data on suspected and confirmed outbreaks. CaliciNet provides genotypic information and epidemiological data from confirmed outbreaks. The CDC’s CaliciNet data page offers a monthly updated “Norovirus U.S. Outbreak Map”.
- NoroSTAT: This real-time reporting network from 14 states offers a more immediate picture of outbreak activity.
- National Respiratory and Enteric Virus Surveillance System (NREVSS): NREVSS provides another layer of data for trend analysis. Data from the week ending December 21, 2024, showed a concerning 22% positivity rate for norovirus tests.
Regional Insights: A Patchwork of Outbreaks (Late 2024 Data)
Regional data from late 2024 shows the geographical distribution of outbreaks:
- United States: Between September 1 and October 21, 2024, California reported the highest number of cases (43), followed by Florida (24), New York (21), and Virginia (20). Other states with significantly elevated figures included Ohio, Wisconsin, and Minnesota (18 each), Rhode Island (16), Oregon (13), West Virginia, and Michigan (11 each).
- Midwest Region (US): For the week ending December 21, 2024, the Midwest region had the highest percentage of positive norovirus cases (26% of 1,509 tests).
- Minnesota: Minnesota experienced a particularly high number of outbreaks, with over 40 reported in December 2024 alone.
Norovirus Seasonality, Transmission, and High-Risk Settings
Norovirus outbreaks typically peak between November and April in the Northern Hemisphere. The virus is highly contagious, spreading through direct contact, contaminated food or water, and contaminated surfaces. It is the leading cause of foodborne illness in the United States. Healthcare facilities, particularly long-term care facilities, are disproportionately affected, accounting for over half of all reported outbreaks. Other high-risk settings include restaurants, schools, childcare centers, and cruise ships.
Practical Takeaways and Actionable Advice
- Robust Hygiene Practices: Stringent handwashing protocols, thorough cleaning and disinfection procedures, and safe food handling practices are paramount.
- Employee Training: Educating employees about norovirus symptoms, transmission, and prevention is essential.
- Outbreak Response Plan: A well-defined plan for managing a potential norovirus outbreak is crucial.
- Data Monitoring: Staying informed about regional norovirus activity through official sources like the CDC and local health departments allows for proactive risk assessment and mitigation.
Conclusion
The 2024-2025 norovirus season demonstrated the unpredictable nature of this highly contagious virus. While a comprehensive, real-time map may not be readily available, understanding the data from various surveillance systems and employing robust prevention strategies are key to mitigating the impact of future outbreaks.