Foodborne Viruses Pose Unique Challenges for Mitigation

Foodborne viruses can be tough to prevent and mitigate. Some can’t be cultured, so they are difficult to analyze. Others aren’t affected even by strong disinfectants, so intervention is ineffective. In the past decade, an additional virus, hepatitis E, joined norovirus and hepatitis A as a top three concern for human food safety.

To tackle these challenging foodborne viruses that can cause serious human illnesses, the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO) are holding a series of meetings focused on microbial risk. The first Joint FAO/WHO Meeting on Microbiological Risk Assessment (JEMRA) convened in September 2023 in Rome and focused on foodborne viruses of top concern for public health, analytical methods, and contamination indicators. The second meeting, which took place in February 2024 in Geneva, discussed prevention and intervention measures for these viruses. A third meeting is planned for later in 2024 and will focus on evaluating risk.

The final reports for the first two meetings are still in progress, with only summaries released so far. Experts involved in the meetings said significant advances have been made in the study of foodborne viruses; these have helped researchers understand the science of viral mitigation since the inaugural JEMRA meeting 16 years ago, a milestone event that was the first time the issue of viruses in foods was brought to international attention.

“We have improved norovirus surrogates and ways to study human norovirus, and we have better detection methods, like digital PCR,” says Kalmia Kniel, PhD, associate chair of the department of animal and food sciences at the University of Delaware in Newark. She adds that thermal treatments are often relied on to inactivate viruses, but there are promising non-thermal technologies being studied, including cold plasma, chlorine dioxide, and some chemical disinfectant combinations.

The Biggest Threats

Dr. Kniel chaired the 2023 meeting and was a member of the expert committee that reviewed recent scientific developments, data, and evidence associated with foodborne viruses. JEMRA will update and provide scientific advice to the Codex Committee on Food Hygiene, which requested the series of meetings. The Codex committee will use the information for its international recommendations and standards. The expert committee also considered trade implications of possible standards to ensure that food safety does not become a trade barrier.

In reviewing viruses associated with human foodborne illness, the expert committee identified human norovirus as the leading cause of viral foodborne illnesses, followed by hepatitis A and hepatitis E. The ranking considered the frequency of illness, the clinical severity of the disease, and the food most often linked to the virus; however, while hepatitis A and hepatitis E were ranked equally behind norovirus in terms of frequency, they were higher than norovirus in terms of clinical severity. The committee lacked sufficient data to rank other viruses, including rotavirus and sapovirus.

In terms of the foods most associated with the viruses as a potential public health threat, prepared food, frozen berries, and shellfish—in that order—are associated with norovirus. For hepatitis A, linked foods are shellfish, frozen berries, and prepared foods. Those two viruses are transmitted via contamination by feces exposure. For hepatitis E, a zoonotic virus, pork and wild game are associated, and the virus is transmitted from animal to human.

The committee considered only water used in food production, in processing, in preparation, or as an ingredient, not water intended only for drinking, in its assessments.

Viral foodborne disease has a substantial impact on morbidity and mortality globally, but surveillance data is sparse, and there is the potential for asymptomatic shedding, so it is difficult to craft prevention and control strategies.