Shigella: Sources, Symptoms and Controls

Shigella is a highly infectious bacterium spread by the faecal-oral route, so even a tiny dose can cause illness. In food businesses it usually reaches customers through an infected food handler with poor hand hygiene, or via produce and water contaminated with human sewage. Control it with strict handwashing, excluding staff who have gastro symptoms, thorough washing of ready-to-eat produce, safe water and thorough cooking. Key takeaways: Shigella has a very low infectious dose, so tiny amounts of faecal contamination on hands, food or equipment can make people ill.. The most common route in food businesses is an infected food handler who does not wash their hands properly after using the toilet.. Ready-to-eat produce and water contaminated with human sewage are the other main sources, so wash produce well and use a safe water supply.. Exclude food handlers with diarrhoea or vomiting from handling food, and follow your regulator's advice on when they may safely return.. Handwashing, cooking to 75°C, keeping cold food at or below 5°C, and preventing cross-contamination together break the chain.. What Shigella is and why it matters Shigella is a group of bacteria that cause shigellosis, a gastrointestinal illness passed on by the faecal-oral route. That means the bacteria travel from the faeces of an infected person into another person's mouth, usually carried on unwashed hands, contaminated food or contaminated water. Humans are the main reservoir, so in a food business the risk almost always traces back to a person rather than to raw meat or animals. How Shigella spreads through food handlers The single most common way Shigella enters food in a business is through an infected food handler with inadequate hand hygiene. After using the toilet, someone carrying the bacteria can transfer them from their hands to ready-to-eat food, utensils or work surfaces. Because the infectious dose is so low, even hands that look clean can carry enough Shigella to make customers ill. Wash hands thoroughly with soap and warm running water, then dry with single-use towel, after every toilet visit. Always wash hands before handling ready-to-eat food and after breaks. Use tongs, gloves or utensils rather than bare hands for ready-to-eat items. Report any diarrhoea or vomiting to a supervisor before starting work. Contaminated produce and water The other major route is fresh produce and water contaminated with human sewage. Fruit and vegetables eaten raw, such as salad leaves, herbs and berries, can carry Shigella if they were grown, washed or handled using contaminated water, or handled by an infected person. Because these foods are not cooked before serving, any contamination present goes straight to the customer. Buy produce from reputable, approved suppliers. Wash ready-to-eat fruit, vegetables and herbs well under clean running potable water. Use only potable water for washing, ice and as an ingredient. Store washed ready-to-eat produce away from raw meat, poultry and unwashed items. Symptoms of shigellosis Shigellosis usually appears a day or two after exposure, though this can vary. Typical symptoms include diarrhoea (which may contain blood or mucus), stomach cramps, fever and nausea. Illness is often more severe than many other forms of gastro, and dehydration is a real risk, particularly in vulnerable people. Practical controls in a food business No single measure controls Shigella on its own; layered controls break the faecal-oral chain at several points. Hand hygiene is the foundation, backed up by excluding ill staff, protecting ready-to-eat food, and preventing cross-contamination between raw and ready-to-eat items. Thorough cooking is highly effective because heat destroys the bacteria. Handwashing after the toilet, before handling food, and between tasks. Exclude food handlers with gastro symptoms from food handling. Cook food thoroughly to 75°C core where cooking is a step. Prevent cross-contamination between raw and ready-to-eat foods. Clean and sanitise surfaces, utensils and hand-contact points regularly. Provide well-stocked handwash basins with soap, warm water and single-use towels. Excluding and returning ill staff Because Shigella spreads so easily and people can remain infectious after symptoms stop, managing unwell staff is one of the most important controls. Food handlers who have diarrhoea or vomiting should not handle food and generally should not be at work in a food-handling role. Under the Food Standards Code, they must report their condition, and the business must take action to prevent contamination. Checklist: Handwash basins stocked with soap, warm running water and single-use towels. Clear rule that staff report diarrhoea or vomiting before their shift. Symptomatic food handlers excluded from food handling. Ready-to-eat produce washed under clean, potable running water. Tongs, gloves or utensils used for ready-to-eat food instead of bare hands. Raw and ready-to-eat foods separated in storage and preparation. Surfaces and equipment cleaned and sanitised on a set schedule. Return-to-work clearances follow medical and health-authority advice. Common mistakes: Assuming that keeping food cold controls Shigella, when the infectious dose is so low the bacteria need not multiply to cause illness. Letting a food handler return straight after symptoms stop, when they may still be shedding bacteria. Relying on a quick rinse to make raw produce safe instead of washing thoroughly and sourcing well. Handling ready-to-eat food with bare hands rather than tongs, gloves or utensils. Under-stocked or hard-to-reach handwash basins that discourage frequent, thorough washing. Using non-potable water for washing produce, making ice or as an ingredient.