Many animals, mainly ruminants like cattle, sheep, and goats, can be colonized by STEC in their gastrointestinal track without showing any symptoms. These microorganisms can be excreted in the faeces, contaminating the animal's coat and causing accidental contamination of food, water, and the environment. Ensuring food hygiene throughout the supply chain is essential to prevent human exposure to these pathogens.
Humans can be infected with STEC as a result of:
Consumption of contaminated food, of both animal and plant origin
Food can be accidentally contaminated with faecal matter, such as during milking or slaughtering. Food can also become contaminated through contact with contaminated work surfaces or by being handled by individuals with gastrointestinal manifestation of STEC infection.
Some foods have a higher risk of contamination and transmission of STEC to humans. Therefore, they should not be consumed by at-risk populations (e.g., children):
- Meat and meat products (e.g., hamburgers, meatballs), especially from beef, if consumed raw or undercooked (the food should reach at least an internal temperature of 70°C for 2 minutes);
- Unpasteurized (raw) milk and dairy products made from raw milk;
- Unwashed and raw vegetables and fruits. These foods can be accidentally contaminated during the growing process through contact with animal or human waste, including contaminated water;
- Unbaked dough from bakery products (e.g., cake batter, creams, pizza dough).
Contact with reservoir animals or contaminated areas
Contact with cattle, sheep, goats, or other domestic or wild ruminants is a significant transmission route of infections to humans, particularly in educational and recreational activities such as farm schools, farmhouse, and petting zoos. The risk of STEC infection is also in the areas where animals live (e.g., grazing areas), as they are often contaminated by animal faeces and manure.
Accidental ingestion of contaminated water
Environmental exposures include bathing waters (e.g., sea, rivers), recreational bathing areas in uncontrolled water bodies (e.g., streams, creeks, wells), and domestic paddling pools, particularly when used by multiple people. Infection can occur by accidentally swallowing water contaminated with faeces with STEC.
Person-to-person transmission
STEC infections can be transmitted from person-to-person through the faecal-oral route. This is common in young children who are not yet fully independent to perform their personal hygiene and is particularly significant in community settings such as families, kindergartens, recreation centres, and nursery schools. In families, young children are the most vulnerable to STEC infections.
