The effect of travel restrictions on the spread of the 2019 novel coronavirus (2019-nCoV) outbreak

Matteo Chinazzi; Jessica T. Davis; Marco Ajelli; Corrado Gioannini; Maria Litvinova; Stefano Merler; Ana Pastore y Piontti; Luca Rossi; Kaiyuan Sun; Cécile Viboud; Xinyue Xiong; Hongjie Yu; M. Elizabeth Halloran; Ira M. Longini; Alessandro Vespignani

The presented analysis, as all modeling exercises, has a number of limitations and assumptions that are worth considering. The model parameters such as generation time and incubation period are chosen based on early results on the 2019-nCoV outbreak and prior knowledge of SARS and MERS coronavirus epidemiology. While we believe that the model is rather stable to variations in these parameters, more information on the key characteristic of the disease would considerably reduce uncertainties. The transmission and mobility model does not account, at this stage, for heterogeneities due to age differences in susceptibility and contact patterns. The calibration of the model does not consider correlations among importations (family travel) and assumes that travel probabilities are homogeneous across all individuals in the catchment area of each transportation hub. We were not able to find reliable data sources on the effectiveness of containment measures in place in Mainland China before Jan 23 (e.g. body temperature screening for departure in Wuhan International airport) which are thus not included in the model. In the travel restriction scenario we assume long term enforcement of individual mobility restrictions (travel was restricted until the end of June 2020). This might not be a feasible nor sustainable policy for such a long period of time.