Temperature, rainfall and vapor pressure lead DF incidence by a lag of 8–10 weeks, constant through time. DF reproductive ratio is increasing through time and displays two clear peaks per year, reflecting the sub-annual periodicity of DF incidence.
DF and relative humidity show both strong seasonality and a sub-annual periodicity. Temperature, rainfall, and vapor pressure show strong seasonality. DF reproductive ratio was calculated from Soper’s formula and smoothed to highlight both its long-term trend and seasonality. Cross-wavelet spectra between DF and each climatic variables were also computed. Wavelet decompositions were used to characterize the main periodic cycles of DF and climatic variables as well as the mean phase angles of these cycles. MethodsĬlinical suspected cases of DF from the 14 central districts of Hanoi were obtained from the Ministry of Health over a 8-year period (2002–2009).
This study aims at characterizing the seasonality of DF in Hanoi and its links to climatic variables as DF incidence increases from year to year. Both DF epidemiology and climate in Hanoi are strongly seasonal. Dengue fever (DF) has been emerging in Hanoi over the last decade.
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