Prevention of emerging (food-borne) enteric viral infections: diagnoses, viability testing, networking and epidemiology
Noroviruses cause gastroenteritis and are notorious for their propensity to cause outbreaks of illness in healthcare settings, restaurants and cruise ships, among others. The DIVINE project was developed to provide meaningful data about the surveillance of this increasingly prevalent disease. While there is a great diversity of noroviruses, both in humans and animals, little was known about the population structure of these viruses in Europe; this knowledge is needed to understand sources and modes of transmission. Therefore, DIVINE was coupled with the research project EVENT to allow more in-depth analysis of the data collected through routine surveillance activities.
Truly integrated virological and epidemiological data collection was successfully accomplished in 10 of the 13 participating countries. Norovirus GII.4 strains were found to be the dominant cause of outbreaks of vomiting and diarrhoea in hospitals and other healthcare settings, whereas a broader diversity was seen in outbreaks in other settings and transmission routes. The real added value of the integrated reporting was the ability to distinguish patterns of outbreaks based on the molecular information. The DIVINE-Net partners found that a substantial proportion of outbreaks is related to food-borne transmission, including diffuse outbreaks resulting from consumption of imported foods. This is of concern because the currently used control mechanisms are insufficient to detect and/or predict presence or absence of viruses in the food chain.
For the successful intervention in the case of diffuse international outbreaks, completeness and timeliness of reporting would need to be improved and expanded to countries that are not currently participating. Following the decision not to continue surveillance of Norovirus outbreaks by the European Centre for Disease Prevention and Control (ECDC), the scientific community agreed to launch a global collaboration following the model developed through this network in order to study the evolution of these viruses in an international context.
Noroviruses are increasingly recognised as a health threat, due to the propensity of these viruses to cause outbreaks in healthcare settings, with occasionally severe impact. In contrast to other disease-specific surveillance networks, the EC cannot rely on data aggregation of laboratory test reports from individual sick patients at national level, because methods for Norovirus detection are not routinely used in many countries.
While epidemiological criteria can be used to identify outbreaks of illness due to Noroviruses (as piloted in the 'Food Borne Viruses in Europe' (FBVE) project), the lack of underpinning laboratory data would result in a surveillance activity of little value for early warning purposes. Timely strain characterisation is essential for detection of emerging novel viral strains and for offering an early warning for the emergence of more aggressive strains.
Therefore, DIVINE-Net set out to build on the collaboration achieved by the FBVE project in which national expertise in virology and epidemiology were combined to strengthen competence in Norovirus outbreak detection and control, and to develop the necessary laboratory tools and databases.
The network managed to develop fully integrated collection and analysis of laboratory and epidemiological data in 10 countries, and comparative analysis without this level of integration for the others. The databases have been filled with data from over 10 000 outbreaks, and have been (and are being) analysed for follow-up questions. Molecular characterisation of outbreak strains was done to provide the basis for a meaningful grouping of circulating viruses, which then was applied in the surveillance.
By doing so, the partners have for the first time in the world demonstrated the unusual dynamics of the most common Norovirus strain (GII.4), which evolves very rapidly in a manner similar to influenza A. It also showed that genotyping information can help dissect food-borne from person-to-person outbreaks, and systematic implementation of this would increase the quality of data collected on food-borne outbreaks.
This is needed, because food-borne outbreaks were found to be common, including diffuse, international outbreaks for which no control system is in place. Also, the European Food Safety Authority (EFSA) has indicated the need for such an outbreak-based surveillance system. Finally, a globally accessible genotyping tool has been made available via the Internet.
At the end of this project, the European Centre for Disease Prevention and Control (ECDC) decided not to continue with norovirus outbreak surveillance.
After discussions concerning this decision in the international scientific community, it was decided to launch a global collaboration to retain some of the expertise and study the evolution of these viruses in a global context. They will use the network to disseminate knowledge to developing countries, and network laboratory information as a tool to alert each other about new strains or otherwise unusual events.
The graph shows the number of outbreaks per month due to norovirus. The colours represent the different genotypes and variants. It clearly shows that GII.4 strains dominate the epidemics and that new GII.4 strains emerge quickly, and are able to fully replace former endemic strains.