Risk assessment of dengue autochthonous infections in Tokyo in summer, especially in the period of the 2020 Olympic Games

Abstract

In Tokyo, Japan, an outbreak of autochthonous dengue fever occurred in summer of 2014. In summer of 2020, when the Olympic Games will be held, a lot of participants and spectators from abroad will visit Tokyo. This study is aiming at analyzing a risk of autochthonous dengue infections in Tokyo in summer and also an additional risk in the Olympiad by using a mathematical model. We developed a stochastic transmission model with the cooperation of seasonal factors which influence much on the transmission cycle of dengue virus, and carried out stochastic simulations for each of the scenarios provided adequately. We found that (1) the incidence of dengue autochthonous infections is predicted to be small number cases; (2) the local climate makes a great influence on a scale of dengue autochthonous infections; (3) the incidence reaches a peak in August and early September; and (4) there is a bare possibility of development into dengue outbreak. In the Olympiad held in summer of 2020, an additional risk of dengue autochthonous infections will amount to about the double of risk in normal years.