Assessing the risk of foodborne viruses at global level

Foodborne viruses, microorganisms so small that they cannot be seen by most microscopes, have an enormous impact on peoples’ health, lives and livelihoods around the world. For example, over 20 percent of all foodborne diarrhoea illnesses and nearly 40 percent of all severe or invasive foodborne diseases are caused by viruses.    

In September, the Joint FAO/WHO Expert Meeting on Microbiological Risk Assessment (JEMRA) convened one of a meeting on foodborne viruses to provide the most recent science to guide an update to the Guidelines on the Application of General Principles of Food Hygiene to the Control of Viruses in Food (CXG 79-2012), which is part of the Codex Alimentarius.  

Experts ranked the viruses causing foodborne diseases, considering both the frequency and severity of illness that they cause. Norovirus was considered to pose the greatest burden to public health. Next on the list were hepatitis A virus and hepatitis E virus. Other viruses transmitted through food with lower impact included rotavirus, sapovirus, enterovirus, astrovirus and enteric adenovirus. 

Viruses can contaminate food at any point in the food chain - from production to consumption. Likewise, almost any food can potentially be a vehicle to transmit viruses. However, the experts highlighted that certain foods are more likely sources of viral infections than others. For example, prepared foods, things like prepared salads or sandwiches that are intended to be eaten without further cooking or preparation, were the most frequent source of norovirus infections, regardless of location. The second most common food associated with norovirus infection was different in different regions of the world, presumably a result of distinct food production or consumption patterns in various parts of the world. Frozen berries have been tracked as the second source of noroviruses in several regions, but in other areas, shellfish was considered the second most significant source of infection. 

Shellfish, frozen berries and prepared foods were also the most common foods associated with hepatitis A virus when viewed from global perspective. Again, substantial regional differences between ranking order importance of these foods were noted. Pork was identified as the primary food source of hepatitis E virus. Wild game is also a source of hepatitis E virus, but to a lesser extent than pork or pork products.   

Foodborne viruses are difficult to isolate in the laboratory and this often presents as a diagnostic challenge. JEMRA experts reviewed the available detection and genetic typing and characterization methods for foodborne viruses. They acknowledged a number of achievements and developments since the publication of the last Codex guideline on the subject. Notably, the sensitivity of detection and the ability to discriminate between different strains of the same virus (typing methods) have greatly improved in the last two decades. In addition, the cost for laboratory analysis is continuously decreasing.  However, there are still limitations to overcome:  With the advent of new techniques, it is sometimes difficult to harmonize the interpretation of results among laboratories using different methods.   

“Knowing what viruses are present in foods and which foods are most commonly contaminated will permit food safety regulators to prioritize where to focus their interventions and control measures to achieve the most impactful return on their investments,” said Kang Zhou, FAO Food Safety Officer.  Future JEMRA meetings will focus on the effectiveness of various interventions to control foodborne viruses, giving policymakers even more information to make science-informed decisions on the control of foodborne viruses applicable to their specific situations and conditions.  

Download the summary report here: 
Joint FAO/WHO Expert Meeting on microbiological risk assessment of viruses in foods. Part 1: Food attribution, analytical methods, and indicators, Summary and conclusions, 2023

Find out more about JEMRA on the FAO website and the WHO website 

Photo: © FAO/Camilo Pareja