Fig. 2: Characteristics of a latitudinal gradient in the periodicity and peak timing of dengue fever epidemics in China.

a Amplitude of the annual periodicity (F = 19.62, P = 0.0001). b Amplitude of the semi-annual periodicity (F = 12.24, P = 0.0016). c Timing of primary annual dengue fever peak, in weeks from 1st January (F = 0.90, P = 0.3514). Colors represent different climatic zones (red = tropical, yellow = sub-tropical, green = warm-temperate, blue = mid-temperate, black = cold-temperate). Symbol size is proportional to the number of dengue cases in each province. The solid black line indicates a linear regression fit (regression weighted by the average annual number of dengue fever cases). The results of the F test and the corresponding P values were employed to testing the significance of the linear regression fit. P values are given on the graphs. d Amplitude of the annual periodicity in each province. e Amplitude of the semiannual periodicity in each province. f Timing for primary annual peak of dengue fever in each province. NA in the legend indicates that the region is temporarily unable to calculate these indicators (No dengue cases are reported in Tibet during the study time, and data for Hong Kong, Macau, Taiwan, Spratly Islands, and other parts of China outside of mainland China are not currently available).