Before revision:  We provide an algorithm, based on a piecewise linear approximation of the logarithm of epidemic observables, allowing one to monitor the epidemic . Our methods combine ideas from several fields of mathematics: tropical geometry, Perron--Frobenius theory , probability and optimization, transport PDE in population dynamics .
After revision:  We provide an algorithm, based on a piecewise linear approximation of the logarithm of epidemic observables, allowing one to detect epidemic resurgences. We rely on a transport PDE epidemiological model, and we use methods from Perron-Frobenius theory and tropical geometry .