There are a number of disease which must be notified when diagnosed by a doctor for example: Dysentery, Typhoid and other food poisonings, Diphtheria, Cerebro-spinal Meningitis, Chicken Pox, Epidemic Parotitis(Mumps), Measles, Pertussis(Whooping Cough), Rubella and Tuberculosis for epidimiogical purposes.

When certain of these diseases are notified the patient is contacted and questioned as to date of onset of symptoms and persons s/he may have been in contact with. This is carried out so as to try to establish the source of the infection and to limit its spread. It may be necessary, especially in the case of food handlers to exclude them from work until certified to be no longer infectious so as to diminish the risk of a food borne disease being transmitted to others. For similar reasons, children too young to be conscious of personal hygiene may be excluded from school while they are infectious.