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Not your typical foodborne disease: When exposure leads to invasive infection

Not your typical foodborne disease: When exposure leads to invasive infection

20/04/2026

Some foodborne hazards do not begin with gastrointestinal symptoms like diarrhea, but instead lead directly to severe invasive disease, including bloodstream infections, joint destruction, and long-term complications even in otherwise healthy adults. This is the reality of Streptococcus agalactiae sequence type 283 (ST283), also known as Group B Streptococcus (GBS), a zoonotic pathogen linked to freshwater fish and aquaculture systems. The comprehensive review “Rethinking Group B Streptococcus: The rise of sequence type 283 as a foodborne zoonotic pathogen”, published in Comprehensive Reviews in Food Science and Food Safety (http://dx.doi.org/10.1111/1541-4337.70471), brings together current evidence on this food safety concern and its broader implications.

Beyond typical foodborne disease

GBS ST283 challenges conventional expectations of foodborne disease. Most foodborne microbiological hazards are associated with gastrointestinal symptoms and are often self-limiting. GBS ST283 presents a fundamentally different profile. It is associated with invasive infections, including meningitis, septic arthritis and bacteremia, and has affected individuals with no underlying health conditions.

Evidence shows that exposure is linked not only to the consumption of contaminated freshwater fish, but also to handling practices along the food chain, expanding the range of possible entry points. This contrast underscores an important shift in perspective: foodborne exposure does not always lead to foodborne disease but can result in foodborne invasive disease.

Freshwater fish: a different risk context

The role of freshwater fish is central to understanding this risk in food. Unlike marine fish commonly used for sushi and sashimi, freshwater fish are not typically consumed raw in many food safety conscious cultures, in part because they are more frequently associated with hazards such as parasites and environmental contamination.

GBS ST283 adds a further dimension to this existing risk landscape. It highlights that, alongside well-recognized parasitic risks, bacterial hazards linked to aquaculture systems and handling practices can also lead to severe outcomes, particularly when fish are consumed raw or undercooked or handled without adequate protection. This context is important for risk communication. The issue is not the consumption of fish per se, but the type of fish, how it is produced, and how it is prepared and handled.

Seeing the invisible: the role of genomic tools

A key aspect underpinning this understanding is the use of whole genome sequencing (WGS). GBS ST283 cannot be reliably distinguished using conventional microbiological methods alone. Its identification depends on sequence-based approaches, which allow differentiation at the level of sequence type and reveal links between human cases, fish, and environmental sources. Through WGS, what might otherwise appear as sporadic or unrelated infections becomes visible as part of a connected pattern across the food chain. This has been critical in recognizing GBS ST283 not simply as a clinical observation, but as a foodborne zoonotic hazard.

Risk profiling in practice

This evolving understanding aligns closely with FAO’s work on risk profiling, particularly for hazards that do not fit neatly into established categories. GBS ST283 illustrates how risk is not defined by exposure alone, but by the combination of severity, transmission complexity, and system-level factors. It sits at the intersection of food production, environmental pathways and human health, with links to aquaculture systems, multiple routes of transmission, and important gaps in data and surveillance. FAO has identified BS ST283 as a hazard requiring structured risk profiling, emphasizing the need to consider not only how often exposure occurs, but also what happens when it does.

A One Health perspective

The review highlights how ST283 moves across humans, fish and aquatic environments, reinforcing the importance of a One Health approach. Freshwater fish act as reservoirs, while environmental conditions and food handling practices contribute to exposure pathways. At the same time, differences in laboratory capacity and access to advanced tools such as WGS influence detection, suggesting that the current picture may not fully capture the scale or distribution of the hazard.

From evidence to action

Despite increasing understanding, key questions remain. How exposure leads to invasive disease is not yet fully understood. The role of asymptomatic human carriage, the absence of quantitative dose–response data, and uncertainties around effective interventions all limit the ability to translate evidence into action. Strengthening access to tools such as WGS, alongside surveillance and data integration, will be essential for supporting risk-based decision making, which remains central to FAO’s food safety work.

Looking ahead

GBS ST283 continues providing a broader and valuable lesson. Foodborne hazards do not always follow familiar patterns. Some are less visible, less frequent, but far more severe in their consequences. At the same time, tools such as whole genome sequencing are making these hazards increasingly visible. Integrating such approaches into food safety systems will be key to ensuring that emerging risks are recognized early and addressed effectively.

To read the comprehensive review: Rethinking Group B Streptococcus: The rise of sequence type 283 as a foodborne zoonotic pathogen

References

FAO. 2021. Risk profile - Group B Streptococcus (GBS) – Streptococcus agalactiae sequence type (ST) 283 in freshwater fish. Bangkok. https://doi.org/10.4060/cb5067en

FAO. 2021. Invasive disease linked to raw freshwater fish: Risk profile - Group B Streptococcus (GBS) Streptococcus agalactiae sequence type (ST) 283 in freshwater fish. Bangkok. https://openknowledge.fao.org/handle/20.500.14283/cb4901en