Food poisoning: causes, symptoms, prevention and distinctions

How it occurs: infection versus intoxication

Broadly, two mechanisms cause foodborne illness. In food infection, live microorganisms in the food—bacteria, viruses, or parasites—colonize or invade the body after ingestion and produce illness. In food intoxication, harmful chemicals or microbial toxins already present in the food cause symptoms even if the producing organism is no longer alive. A short guide to these forms is available at toxic vs infectious forms.

Common agents and examples

Several groups of organisms and substances are frequently implicated. Bacterial causes include species such as Salmonella, Campylobacter, Escherichia coli and Listeria; see general information on bacteria at bacterial causes. Viral agents, notably norovirus and hepatitis A, are common sources of outbreaks—more on viruses at viral causes. Parasites such as Giardia and Toxoplasma can contaminate food or water; background on parasitic contamination is at parasites and food. Rarely, abnormal proteins called prions can cause severe brain disease linked to contaminated meat—basic notes are at prion‑related illness. Some cases result from toxins: examples include botulinum toxin, aflatoxins from mould, or staphylococcal enterotoxins; see toxins at toxic agents.

Symptoms, diagnosis and course

Typical symptoms appear from hours to days after exposure depending on the cause. Sudden vomiting with rapid onset is characteristic of some toxins, while bacterial infections may produce fever, bloody diarrhea or longer incubation periods. Diagnosis relies on clinical history, timing of symptoms, and sometimes laboratory testing of stool, blood or suspected food. Guidance on how infection develops and is identified is at infection and detection.

Prevention and management

• Practice thorough handwashing and good kitchen hygiene to avoid cross‑contamination.
• Cook foods to safe temperatures and refrigerate perishables promptly.
• Use safe water and avoid high‑risk foods for susceptible groups (unpasteurized dairy, undercooked meats, raw shellfish).
• When ill, stay hydrated; seek medical care for severe symptoms, high fever, persistent vomiting, or signs of dehydration.

Impact, history and notable facts

Foodborne illness is a major public health concern worldwide. Outbreak investigations have guided improvements in food production, storage, and inspection practices. While most cases are self‑limited, periodic outbreaks have prompted regulatory change and consumer guidance. Distinguishing infection from intoxication helps clinicians predict onset and guide public health responses. For more authoritative prevention and reporting advice, consult local health agencies and food safety resources provided by public health authorities.