Relationship between increase rate of human plague in China and global climate index as revealed by cross‐spectral and cross‐wavelet analyses

Abstract

Plague has caused the death of hundreds of millions of people throughout the human history. Today this disease is again re-emerging and hence is again becoming an increasing threat to human health in several parts of the world. However, impacts of global climate variation (e.g. El Nino and Southern Oscillation [ENSO]) and global warming on plagues are largely unknown. Using cross-spectral analysis and cross-wavelet analysis, we have analyzed the relationship between increase rate of human plague in China during 1871-2003 and the following climate factors (as measured by the Southern Oscillation Index [SOI], Sea Surface Temperature of east Pacific equator [SST] and air Temperature of the Northern Hemisphere [NHT]). We found in the frequency domain that increase rate of human plague was closely associated with SOI and SST. Cross-spectral analysis reveals that significant coherencies between increase rate of human plague and ENSO were found over short periods (2-3 years), medium periods (6-7 years) and long periods (11-12 years, 30-40 years). Cross-wavelet analysis reveals that increase rate of human plague oscillates in phase with SOI, but in anti-phase with SST over periods of 2-4 years and approximately 8 years (6-10 years). These results indicate that ENSO-driven climate variation may be important for occurrences of human plague in China. However, there is a need for a further analysis of the underlying mechanism between human plague in China and ENSO.