The infection can come from bacteria, viruses or parasites. The infection can occur during food production or by incorrect handling of food in the home kitchen. Symptoms can start within hours of eating contaminated food and include abdominal pain, vomiting and later diarrhoea that sometimes can contain blood. The symptoms usually resolve within 24 hours and usually symptoms are mild. Severe cases can occur and occasionally patients are admitted to hospital. More serious forms of bacterial infection include infection with Campylobacter jejuni that can cause severe pain and diarrhoea containing blood or E. Coli or Salmonella typhi that cause similar symptoms. There are also common viral causes including Norovirus or Rotavirus that can be contracted through raw food or from a food handler. Dehydration can occur in those with prolonged vomiting and diarrhoea and this can be prevented by the use of oral rehydration salts that are available over the counter at a pharmacy. Food poisoning is usually prevented by following safety rules: washing of hands and kitchen surfaces, keeping raw foods separate from ready-to-eat foods, freezing and defrosting foods according to instructions and cooking foods to correct temperatures.