RESUMO
We present evidence that the El Niño phenomenon intensifies the annual cycle of malaria cases for Plasmodium vivax and Plasmodium falciparum in endemic areas of Colombia as a consequence of concomitant anomalies in the normal annual cycle of temperature and precipitation. We used simultaneous analyses of both variables at both timescales, as well as correlation and power spectral analyses of detailed spatial (municipal) and temporal (monthly) records. During "normal years," endemic malaria in rural Colombia exhibits a clear-cut "normal" annual cycle, which is tightly associated with prevalent climatic conditions, mainly mean temperature, precipitation, dew point, and river discharges. During historical El Niño events (interannual time scale), the timing of malaria outbreaks does not change from the annual cycle, but the number of cases intensifies. Such anomalies are associated with a consistent pattern of hydrological and climatic anomalies: increase in mean temperature, decrease in precipitation, increase in dew point, and decrease in river discharges, all of which favor malaria transmission. Such coupling explains why the effect appears stronger and more persistent during the second half of El Niño's year (0), and during the first half of the year (+1). We illustrate this finding with data for diverse localities in Buenaventura (on the Pacific coast) and Caucasia (along the Cauca river floodplain), but conclusions have been found valid for multiple localities throughout endemic regions of Colombia. The identified coupling between annual and interannual timescales in the climate-malaria system shed new light toward understanding the exact linkages between environmental, entomological, and epidemiological factors conductive to malaria outbreaks, and also imposes the coupling of those timescales in public health intervention programs.
Assuntos
Clima , Surtos de Doenças/estatística & dados numéricos , Malária Falciparum/epidemiologia , Malária Vivax/epidemiologia , Animais , Colômbia/epidemiologia , Ecologia , Doenças Endêmicas/estatística & dados numéricos , Meio Ambiente , Humanos , Incidência , Tempo (Meteorologia)Assuntos
Países em Desenvolvimento , Ciência , Orçamentos , Colômbia , Economia , América Latina , Pobreza , Editoração , Ciência/economiaRESUMO
The interannual variation in malaria cases in Colombia between 1960 and 1992 shows a close association with a periodic climatic phenomenon known as El Niño Southern Oscillation (ENSO). Compared with other years, malaria cases increased by 17.3% during a Niño year and by 35.1% in the post-Niño year. The annual total number of malaria cases is also strongly correlated (r = 0.62, P < 0.001) with sea surface temperature (SST) anomalies in the eastern equatorial Pacific, a principal parameter of ENSO. The strong relation between malaria and ENSO in Colombia can be used to predict high and low-risk years for malaria with sufficient time to mobilize resources to reduce the impact of epidemics. In view of the current El Niño conditions, we anticipate an increase in malaria cases in Colombia in 1998. Further studies to elucidate the mechanisms which underlie the association are required. As Colombia has a wide range of climatic conditions, regional studies relating climate and vector ecology to malaria incidence may further improve an ENSO-based early warning system. Predicting malaria risk associated with ENSO and related climate variables may also serve as a short-term analogue for predicting longer-term effects posed by global climate change.