Outbreak is a movie about the spread of a dangerous virus in a small town. The outbreak causes the people to turn against each other and it also threatens their children. The film makes good use of the scientific method to analyse an outbreak. It simultaneously uses epidemiological, microbiological and toxicological methods to develop and test hypotheses about the underlying cause of an outbreak.
An outbreak of disease occurs when the number of cases exceeds that expected in a community, geographical area or season. These events are maintained by infectious agents that spread directly from person to person, through animal reservoirs or via insect or vector transmission and nearly always involve human behaviours that promote or facilitate spread (Table 1).
Epidemics are generally maintained by a small percentage of infective individuals. Changing the behaviour of this percentage can have a significant impact on epidemic control. This is particularly true for re-emerging and emerging diseases such as plague, diphtheria, Ebola, dengue, monkeypox, chikungunya, SARS and MERS coronavirus.
Detecting and identifying an outbreak requires a rigorous epidemiological investigation. The investigator must define the cases, collect data and describe them in terms of time, place and affected persons. A case definition should be specific to the outbreak under investigation and include a description of the underlying source of the disease. Geographical information can be used to present the spatial distribution of cases and under some circumstances it may help to identify clustering.