In the two previous study sessions you have learned about microorganisms and food contamination. The single method of transmission of foodborne diseases to human beings is through ingestion (eating) of food in the following categories:

Raw or undercooked meat and meat products
raw milk (that is, milk that has not been pasteurised or sterilised)
food items contaminated with human faeces (directly or indirectly)
raw vegetables contaminated with soil
food contaminated by chemicals, e.g. pesticides such as malathion
food prepared using contaminated water, e.g. for washing vegetables
food kept in an unsuitable condition for a long time after preparation
poisonous plants.

Why is it unwise to eat food that has been kept for a long time after it was prepared?

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It may have been kept in conditions that created a favourable environment for the growth and multiplication of microorganisms in the food, especially if it was exposed to flies, cockroaches, etc., or kept at a warm temperature.