A notifiable infection, intoxication or illness (MADO – maladie à déclaration obligatoire) can be a significant health problem related to biological, chemical or physical exposure. Therefore, public health protection must be carried out in a timely manner to prevent future cases from occurring. Intervention is aimed at individuals and is carried out for the benefit of the community or a group of individuals. Protecting the health of the population requires constant vigilance and being able to act quickly in the event of a threat to health, whether real or anticipated. For example, syphilis, chlamydia and measles are diseases or infections that are part of MADOs.
Some MADOs are subject to an epidemiological investigation. A nurse usually carries out the epidemiological investigation. They will complete a questionnaire and collect information from the infected person, his/her family or relatives and, if necessary, from the reporting or treating doctor. The information requested includes the diagnosis of the disease, symptoms, complications, laboratory results and analysis, vaccination status, individuals who may be considered close contacts and the search for an epidemiological link with another infected person.
Other than the monitoring of infectious diseases in general, several epidemiological investigations do not require any immediate public health intervention. The link established between some investigations help identify threats to the health of the population and appropriate actions to take.
In some situations, preventive treatment (antibiotics) and vaccination may be recommended for people in close contact with the infected person. Preventive treatment is designed to stop the transmission of the disease and protect individuals who are more at risk.