To use information for decision making epidemiologists need to organise the data collected in a standard format that allows summarising many observations. Data organisation and graphical presentation also serve the purpose of communicating results to various audiences. As the saying goes, a picture is worth a thousand words. On the other hand, this is true only if the illustration in question is thought through and constructed properly, otherwise the graphic may just hide a thousand words. So presenting epidemiological data is a rigorous task and, even if there are no fixed rules, some guiding principles can be defined.
The task may start from any type of dataset. For example a line listing of data collected by means of a questionnaire during an outbreak investigation or from a national surveillance dataset. As a first step in examining the data consider the type of variables in the dataset. The type of variables, and what you would like to show (e.g. distribution or comparison) would guide the choice of method of data display. Tables and graphs, charts or diagrams facilitate description and interpretation of distributions, trends as well as relationships in the data and complement arguments presented in the text. Maps are used to display geographical or place data. Today's powerful computer tools simplify data display and analysis to a great degree.