Do Aedes aegypti lead to larger-scale and more severe epidemic than Aedes albopictus?

Abstract

Background: Taiwan belongs to both tropical and subtropical climate zones, which results in distinctions of spatial distribution between vectors and cases of human infection of dengue. The vectors of dengue in Taiwan comprise Aedes albopictus (distributed island-wide) and Aedes aegypti (located in southern Taiwan). The aims of this study were to (1) find out similarities and differences in epidemiologic characteristics between indigenous dengue cases in southern and other regions of Taiwan, and (2) compare case fatality rates and incidence rates of dengue cases in outbreak cities in southern and non-southern Taiwan. Methods and materials: The data was obtained from Taiwan centers for disease control. Demographic data was from statistics of Ministry of Interior. Epidemiologic characteristics, case fatality rates and incidence rates of 733 indigenous dengue cases from Aedes albopictus prevalent regions (Taipei, New Taipei, Taichung, and Taoyuan Cities) and 74309 indigenous dengue cases from southern Taiwan (Kaohsiung, Tainan, and Pingtung Cities) during 1998–2019 were analyzed by SAS 9.4 and QGIS 3.8. Results: Dengue clusters were frequently detected in southern Taiwan, while cases in other regions were more likely to be sporadic. Age distribution for cases in southern Taiwan and other regions peaked at 50–59 years (N = 13576, 18.27%) and 30–39 years (N = 159, 21.69%), respectively with statistical significance (p < 0.001). The percentage of male dengue patients in southern Taiwan was significantly lower than those in other regions [N = 36685 (N = 49.37%) vs. N = 403 (54.98%)] (p < 0.0025). Case fatality rates (CFRs) of dengue in southern Taiwan in 2002, 2014, 2015, and 2016 were 0.36%, 0.14%, 0.53%, 1.30%, much higher than CFR in Aedes albopictus prevalent area. Incidence rate of indigenous cases per 100 thousand population in southern Taiwan in 2002, 2014, 2015, and 2016 (95.57, 279.03, 778.90, 6.78) were much higher than those in other regions (0.26, 0.43, 2.55, 0.05). Conclusion: Dengue in Aedes aegypti-affected areas resulted in larger-scale and more severe epidemics involving more numbers of clusters than in areas with only Aedes albopictus. Therefore, more active surveillance and early detection of dengue cases in Aedes aegypti distributed areas is needed.