An alarming trend in Europe since 2021
Norovirus, a highly contagious pathogen known for causing gastroenteritis outbreaks, has been a persistent concern in the domain of food safety. Recent reports have highlighted an alarming trend - an increase in notifications of norovirus cases out of season, raising questions about the sources and routes of contamination. According to the latest One Health zoonoses technical report from European Food Safety Authority (EFSA) and European Centre for Disease Prevention and Control (ECDC), Norovirus in fish and fishery products have been listed as the agent/food pair associated with the highest number of outbreaks in humans in the EU in 2022 1.
In 2022, norovirus (and other calicivirus) was the third most frequently reported cause of foodborne outbreaks in the EU, with a significant increase in cases and outbreaks compared to 2021 (11.6%). Most cases occurred in France, and it was the main causative agent in several countries including Denmark and Finland. Despite the rise in cases, hospitalizations decreased. Norovirus was responsible for the highest number of human cases overall, with many large outbreaks linked to various food commodities and settings. Twelve outbreaks involved over 100 cases each, but only five were confirmed with strong evidence. Switzerland also reported one large outbreak 1.
Understanding Norovirus Contamination in Food
Norovirus is notorious for its ability to spread rapidly in settings where people gather, such as cruise ships, schools, and restaurants. However, its presence in food samples has added another dimension to its transmission dynamics. Contaminated food, whether from improper handling, contaminated water sources, or infected food handlers, can serve as a vehicle for norovirus to enter our gastrointestinal tracts. Raw foods like salads, frozen fruits, mollusks as well as drinking water can be contaminated with Noroviruses and lead to infections. Noroviruses are non-enveloped, RNA viruses belonging to the Caliciviridae family. These are classified into 10 genogroups (GI-GX) based on the VP1 protein, with genogroups I, II, and IV being the most significant for human infections 2. Among these, the GII genotype is known for causing the most severe outbreaks and has been responsible for several pandemic strains 2. The virus high mutation rate allows it to evade the immune system and persist in the population, leading to frequent reinfections.
Research studies, including a recent investigation in the Tuscany region of Italy, have shed light on the prevalence of norovirus contamination in food samples. The analysis of original notifications in the Rapid Alert System for Food and Feed (RASFF) over a seven-year period from 2015 to 2021 has provided valuable insights into the scope of the issue and the need for improved detection and prevention strategies 3. Notably, norovirus was detected in 50% of the bivalve mollusks and products thereof notified for pathogenic micro-organisms.
The Challenge of Out-of-Season Norovirus Cases
One particularly concerning observation is the unexpected increase in RASFF notifications related to norovirus cases occurring out of season in 2024. Traditionally, norovirus outbreaks have been associated with the winter months, earning it the nickname "winter vomiting bug." However, the increased reporting of cases in other seasons suggests a shift in the patterns of norovirus circulation and highlights the need for heightened vigilance year-round.
The unexpected increase in norovirus cases outside the typical winter season in 2024 could be due to several factors:
1. Environmental Changes: Shifts in climate and weather patterns can affect the survival and transmission of viruses. Warmer temperatures and changes in humidity might be creating conditions that allow norovirus to thrive outside its usual season.
2. Human Behavior: Changes in human behavior, such as increased travel, gatherings, and changes in hygiene practices, can influence the spread of the virus. Post-pandemic behaviors might also play a role, as people resume activities that were previously restricted.
3. Virus Evolution: Norovirus, like other viruses, can mutate. These mutations might result in strains that are more resilient to environmental conditions or more easily transmissible year-round.
4. Surveillance Improvements: Enhanced surveillance and reporting systems, such as the RASFF, might be detecting more cases that would have previously gone unreported.
These factors combined suggest that norovirus is adapting to new conditions, making it essential to maintain vigilance and adapt public health strategies accordingly.
Introducing the InviScreen® Norovirus Detection Kit
In the face of emerging challenges posed by norovirus contamination in food and the rise in out-of-season cases, proactive measures are crucial to safeguard public health. The InviScreen® Norovirus Detection Kit from Invitek Diagnostics offers a cutting-edge solution for the rapid and accurate detection of norovirus genogroups I (GI) and II (GII) in food samples.
This state-of-the-art kit leverages real-time Reverse Transcription Polymerase Chain Reaction (RT-PCR) technology, a gold standard method in molecular diagnostics, to deliver precise results in a timely manner. By adhering to the rigorous standards set by ISO 15216, the InviScreen® kit ensures reliable and sensitive detection of norovirus, empowering food safety professionals to identify contamination sources and take swift corrective actions.
Embracing a Proactive Approach to Food Safety
As we navigate the challenges of norovirus contamination in food samples and the evolving landscape of norovirus outbreaks, it is imperative to equip ourselves with reliable tools that enable effective surveillance and response. By advocating for the adoption of advanced detection methods such as the InviScreen® Norovirus Detection Kit, we can enhance our ability to protect consumers and uphold the integrity of our food supply chain.
Together, let's prioritize food safety and strive for a future where norovirus outbreaks are mitigated through proactive measures and cutting-edge technologies.
References
[1] European Food Safety Authority; European Centre for Disease Prevention and Control. The European Union One Health 2022 Zoonoses Report. EFSA J. 2023 Dec 12;21(12):e8442. doi: 10.2903/j.efsa.2023.8442.
[2] Savini F, Giacometti F, Tomasello F, Pollesel M, Piva S, Serraino A, De Cesare A. Assessment of the Impact on Human Health of the Presence of Norovirus in Bivalve Molluscs: What Data Do We Miss? Foods. 2021 Oct 14;10(10):2444. doi: 10.3390/foods10102444.
[3] Giusti A, Galgani M, Barontini F, Balocchini E, D'Ascenzi C, Armani A. Analysis of the original notifications in the Tuscany region "Rapid Alert System for Food and Feed" in the seven-year period 2015-2021. Ital J Food Saf. 2024 Apr 4;13(2):12341. doi: 10.4081/ijfs.2024.12341.
