The Estimation of Imported Dengue Virus From Thailand

BackgroundDengue fever is one of the important causes of illness among travelers returning from Thailand. The risk of infection depends on the length of stay, activities, and arrival time. Due to globalization, there is a concern that infected travelers may carry dengue virus (DENV) to their country of residence and cause an outbreak. MethodsTo estimate the infective person-days of travelers returning from Thailand, we developed a model with the following parameters: the probability of travelers being infected, number of arrivals, length of stay of travelers, incubation period, and duration of the infective period. The data used in this study were the dengue incidences in Thailand during 2004-2013 and foreign traveler arrivals in 2013. ResultsWe estimated the highest infective person-days for each country group. The highest value was from June to August during the rainy season in Thailand for all groups. Infective person-days ranged from 87 to 112 per 100,000 travelers each year. ConclusionOur results provided a fundamental step toward estimation of the risk of the secondary transmission of DENV in non-epidemic countries via travelers, which can serve as an early warning of a dengue outbreak. The highest infective person-day is associated with the rainy season in Thailand. The increasing number of overseas travelers may increase the risk of global transmission of the DENV. Better understanding of the virus transmission dynamics will enable further quantitative predictions of epidemic risk.