Background Dengue is the most rapidly spreading disease caused by a mosquito-borne virus in the world. The incidence of dengue globally has increased 30-fold in the last 50 years. Understanding the prevalence of dengue and its longitudinal trends can improve prevention and control strategies. This study assessed the trends in prevalence of dengue in Taiwan by population characteristics and geographical region. Methods Dengue and population data for the years 2010–2015 were obtained from the public statistics databases of the Taiwan Centers for Disease Control and Department of Statistics, Taiwan Ministry of Interior. Yearly prevalence rates of dengue were calculated by age group, sex, and administrative area within five geographic regions (northern, mid-western, southern, and eastern regions, and outer islands). Results The national prevalence rate of dengue decreased gradually from 8 to 4 per 100 000 population between 2010 and 2013, but it increased substantially in 2014 and 2015 to 67 and 187 per 100 000 population, respectively. There was no significant difference in prevalence rate between males and females. People aged 60–69 years had a significantly higher prevalence rate than those in the other age groups during 2010–2014, and people aged over 70 years had the highest rate in 2015 (309 per 100 000 population). The southern region had the highest yearly dengue prevalence rate (the rate decreased from 23 to 9 per 100 000 population between 2010 and 2013, but increased to 220 and 616 per 100 000 population in 2014 and 2015, respectively). Three unexpected outbreaks of dengue were observed during the study period: the first outbreak occurred in Penghu County in 2011 (prevalence rate 101 per 100 000 population), the second in Kaohsiung City in 2014 (prevalence rate 540 per 100 000 population), and the third in Tainan City in 2015 (prevalence rate 1208 per 100 000 population). Conclusions More efforts are still needed to prevent and control dengue in Taiwan. The government should direct resources and interventions to southern Taiwan, which has a tropical climate and a high population density, and should target older people who are more likely to be infected. Strategies are also needed to respond quickly to unexpected incidents to prevent dengue outbreaks.
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