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**Making an epidemic curve (epicurve)**

Preben Aavitsland (with a lot of help from Katarina Alpers, RKI)

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**The epidemic curve Time components of an outbreak Shows**

Start End Duration Peak Outliers Helps to form hypotheses on Route of transmission Probable exposure period Incubation time

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The epidemic curve

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**The epidemic curve Histogram X-axis = time Y-axis = number of cases**

Area proportional to number No space between columns One population X-axis = time Start before epidemic, continue after Interval < 1/4 of incubation period Y-axis = number of cases Usually one square = one case Easy to make in Excel

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**Point source 20 15 10 5 No of cases Time Duration ~ Incubation time**

Einmalige Exposition+gemeinsame Quelle Time Duration ~ Incubation time

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**Continous source 20 15 10 5 No of cases Weeks 1 4 7 13 16 19 22 25 28**

5 10 15 20 1 4 7 13 16 19 22 25 28 31 34 37 No of cases Weeks Mean IP

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**Intermittent source No of cases Time (days) 10 9 8 7 6 5 4 3 2 1 1 2 3**

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Time (days)

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**Human to human transmission**

No of cases 10 Generation time 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Zeit

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**Probable exposure time**

No of cases Median incubation time (Intervall between first and last disease onset) 2 15 3 10 5 Punktquelle 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Time 1 Probable exposure time 50% % Median onset time

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**Probable exposure period**

No of cases 20 18 maximum incubation time 16 14 12 10 minimum incubation time 8 6 4 2 1 3 5 1 2 7 3 4 9 5 11 6 7 13 8 15 9 10 17 11 12 19 13 21 14 15 23 16 17 25 18 19 27 20 29 21 22 31 Time Probable exposure period

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**Two ways of making epicurves in Excel**

The ”square method” Turn a work sheet in to squares Fill in each patient as a square The ”chart method” Make a table of onset times Use the chart wizard Make a histogram (by removing intervals between bars in a bar chart)

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MULT. INTEGERS 1. IF THE SIGNS ARE THE SAME THE ANSWER IS POSITIVE 2. IF THE SIGNS ARE DIFFERENT THE ANSWER IS NEGATIVE.

MULT. INTEGERS 1. IF THE SIGNS ARE THE SAME THE ANSWER IS POSITIVE 2. IF THE SIGNS ARE DIFFERENT THE ANSWER IS NEGATIVE.

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