Epidemic malaria in India's Thar desert

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

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.

Malaria's indirect contribution to all-cause mortality in the Andaman Islands during the colonial era

Malaria has a substantial secondary effect on other causes of mortality. From the 19th century, malaria epidemics in the Andaman Islands' penal colony were initiated by the brackish swamp-breeding malaria vector Anopheles sundaicus and fuelled by the importation of new prisoners. Malaria was a major determinant of the highly variable all-cause mortality rate (correlation coefficient r(2)=0.60, n=68, p<0.0001) from 1872 to 1939. Directly attributed malaria mortality based on post-mortem examinations rarely exceeded one-fifth of total mortality. Infectious diseases such as pneumonia, tuberculosis, dysentery, and diarrhoea, which combined with malaria made up the majority of all-cause mortality, were positively correlated with malaria incidence over several decades. Deaths secondary to malaria (indirect malaria mortality) were at least as great as mortality directly attributed to malaria infections.