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When is the outbreak occurring ?
The occurrence of new cases of the disease over time is described as the temporal pattern of disease .
Time based information is collected and organised to find answers to the following questions :
• When did the outbreak begin ?
• What is the pattern of disease over time ?
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• What is the most likely period of introduction / exposure ? ( see Step 3 )
• Are there seasonal or cyclical patterns of disease apparent over longer periods of time ?
The epidemic curve
Epidemic curves are very important in the initial stages of an outbreak and can be created using spreadsheet software such as “ Microsoft Excel ” or specialised programs . The curve provides a visual representation of the magnitude of the event and the rate at which new cases are occurring . They also help monitor efficacy of control measures .
There can be five stages in an epidemic curve as shown in Figure 9 .
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