Viruses represent a significant and evolving challenge to global food safety, responsible for an estimated 600 million foodborne illnesses annually according to the World Health Organization. While norovirus, hepatitis A virus (HAV), and hepatitis E virus (HEV) dominate reported outbreaks, scientific attention is increasingly focused on other viruses with emerging foodborne transmission potential. These pathogens exploit gaps in surveillance, complex food supply chains, and environmental contamination pathways.
Established Threats with Evolving Dynamics
Norovirus remains the leading cause of viral foodborne illness globally, responsible for approximately 125 million cases yearly. Its extreme environmental persistence, low infectious dose (as few as 100 particles), and high shedding concentration in feces (up to 10¹⁰ particles per gram) facilitate spread through contaminated water, fresh produce like berries and leafy greens, and ready-to-eat foods handled by infected workers. Similarly, HAV continues to cause outbreaks linked to contaminated shellfish, frozen berries, and fresh produce, with its prolonged incubation period (10-50 days) complicating tracebacks. HEV, particularly genotypes 3 and 4, exemplifies a zoonotic emergence: endemic in global pig populations, it transmits through undercooked pork products and has caused increasing non-travel-related infections in Europe and Asia. Detection of infectious HEV in commercial pork livers underscores this farm-to-table risk.
Emerging Zoonotic Concerns
Several animal viruses demonstrate documented or theoretical foodborne transmission routes to humans. Nipah virus, carried by fruit bats, can contaminate date palm sap and fruit via bat secretions, causing severe encephalitis in humans. Tick-borne encephalitis virus (TBEV) transmits through unpasteurized milk from infected goats, sheep, or cows, with cases reported across Europe and Asia. While primarily respiratory pathogens, coronaviruses including SARS-CoV-2 exhibit traits relevant to foodborne spread: prolonged fecal shedding, environmental stability on surfaces like stainless steel and plastic, and survival under refrigeration. Though epidemiological evidence for foodborne coronavirus transmission remains lacking, outbreaks in seafood processing facilities highlight the vulnerability of food systems to viruses introduced via human carriers. The H5N1 avian influenza virus has also been detected in poultry muscle tissue and eggs, raising theoretical concerns about undercooked products, though respiratory exposure dominates transmission.
Seafood as a High-Risk Pathway
Filter-feeding shellfish (oysters, mussels, clams) concentrate human and animal viruses from contaminated waters. Studies in European markets detected norovirus in oysters at concentrations up to 10⁶ genome copies per gram. Hepatitis A virus can concentrate 100-fold in oyster tissues from polluted water, while emerging viruses like Aichi virus have also been detected in seafood. Traditional depuration methods show limited efficacy, reducing HAV by only about 1.1 log units on average.
Prevention Challenges and Strategies
Controlling foodborne viruses is complicated by their resistance to heat, freezing, and sanitizers. HAV survives 60°C for one hour, requiring 98°C for complete inactivation, while norovirus retains infectivity after 60°C for 30 minutes. Emerging technologies like atmospheric pressure plasma and gamma irradiation (3-10 kGy) show promise for viral reduction in sensitive products like raw seafood. Strict implementation of Good Agricultural Practices (GAP), Good Manufacturing Practices (GMP), and Good Hygiene Practices (GHP) across supply chains remains fundamental to minimizing contamination from harvest to handling. Enhanced wastewater treatment near agriculture and shellfish beds is critical for reducing environmental viral loads.
Continued surveillance using advanced molecular methods and a One Health approach, integrating human, animal, and environmental monitoring, is essential for detecting emerging foodborne viral threats early. The persistent evolution of these pathogens demands ongoing awareness in food safety systems worldwide.
