epidemic curve epidemic curve an epidemic curve, also known as an epi curve or epidemiological curve, is a statistical chart used in epidemiology to visualise the onset of a disease outbreak. it can help with the identification of the mode of transmission of the disease. it can also show the disease's magnitude, whether cases are clustered or if there are individual case outliers, its trend over time, and its incubation period. it can give outbreak investigators an idea as to whether an outbreak is likely to be from a point source (such as from a food handler), a continuous common source (with ongoing contamination), or a propagated source (that is transmitted primarily between people). for broader coverage of this topic, see mathematical modelling of infectious disease. epidemic curves generally show the frequency of new cases compared to the date of disease onset. examples hepatitis a common source outbreak of hepatitis a in nov-dec 1978 this epidemic curve shows a presumed first case, known as the index case on november 6, 1978. 4 days later, there was a steep increase in cases, followed by the curve tapering down to zero. some cases were food handlers, and some secondary cases. it showed that this is probably a common source outbreak. sometimes, cases could have been exposed days or weeks prior, and diseases with longer incubation periods would flatten these epidemic curves and lower the peaks. covid-19 pandemic