| Sammanfattning: | A key challenge for public health policy makers is determining when an infectious disease
outbreak has finished. Following a period without cases, an estimate of the probability that no
further cases will occur in future (the end-of-outbreak probability) can be used to inform
whether or not to declare an outbreak over. An existing quantitative approach, based on a
branching process transmission model, allows the end-of-outbreak probability to be
approximated from disease incidence time series, the offspring distribution and the serial
interval distribution (the Nishiura method). Here, we show how the end-of-outbreak
probability under the same transmission model can be calculated exactly if data describing
who-infected-whom (the transmission tree) are also available (e.g., from contact tracing
studies). In that scenario, our novel approach (the traced transmission method) is
straightforward to use. We demonstrate this by applying the method to data from previous
outbreaks of Ebola virus disease and Nipah virus infection. For both outbreaks, the traced
transmission method would have determined that the outbreak was over quicker than the
Nishiura method. This highlights that collection of contact tracing data and application of the
traced transmission method may allow stringent control interventions to be relaxed quickly at
the end of an outbreak, with only a limited risk of outbreak resurgence.
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