Study finds link between malaria outbreaks and El Nino events in the country
There were strong indications in the research that El Nino years pose an increased risk for malaria epidemics in the September-December period in central, western and northern highlands of Ethiopia following the Kiremt rainy season. Photo: iStock This year’s El Nino climate event, combined with warming from climate change, could cause a rise in malaria cases in Ethiopia, new research suggests. The country has a history of climate-related malaria outbreaks and the study has corroborated that malaria upsurges in the country often follow El Nino events.
El Nino is the warmer-than-normal phase of the El Nino Southern Oscillation (ENSO) phenomenon, during which the sea surface temperatures (SST) in a region of the equatorial Pacific Ocean become warmer than the average by 0.5 degree Celsius or more.
The World Meteorological Organization July 4, 2023 declared the onset of El Nino conditions in the equatorial Pacific Ocean. The United Nations agency warned of extreme weather events such as heat waves and droughts along with rise in global atmospheric and oceanic average temperatures.
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The study published in Malaria Journal found that El Nino events are strongly related to higher temperatures across the country, drought in north-west Ethiopia during the July–August–September rainy season and unusually heavy rain in the semi-arid south-east during October–November–December (OND).
The rainfall season from July to September is the main one and is known as Kiremt.
Malaria epidemics mostly occur in the country following Kiremt, the researchers found. Widespread epidemics are commonly associated with El Nino events when the maximum recorded temperature at a given station on a given day, also called Tmax, is high and drought is common.
In Amhara — Ethiopia’s second biggest region — malaria epidemics were not associated with ENSO, but with warm Tropical Atlantic SST and higher rainfall.
Malaria-climate associations in Ethiopia were assessed by the researchers led by Adugna Woyessa using monthly climate data (1981–2016) from the Ethiopian National Meteorological Agency (NMA), SSTs from the eastern Pacific, Indian Ocean and Tropical Atlantic and historical malaria epidemic information obtained from the literature.
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Data analysed spanned 1950–2016. During the periods of analysis 1991–2014 for rainfall and temperature, respectively, El Nino’s impact on rainfall and temperature was strongest over the north-western half of the country during July-September when the probability of low rainfall is high.
In the OND period, El Nino years have a higher probability of high rainfall in south-east Ethiopia.
Local and widespread epidemics can occur in any ENSO phase, but there were strong indications that El Nino years pose an increased risk for malaria epidemics in the September-December period in central, western and northern highlands of Ethiopia following the Kiremt rainy season.
Higher temperatures and rainfall are important factors in driving epidemics at a local and regional level. The cyclical nature of El Nino (2–7 years) means that a global event is likely in the coming years following an extended La Nina period, cautioned the researchers.
The health system in Ethiopia is adversely affected by the civil conflict in the northernmost region of Tigray, along with the projected warming trends and fluctuation of rainfall. This should alert malaria control managers to the likely climate risks to achieving malaria elimination.
Read more: Climate change and malaria
Malaria control managers should be alert to any warnings of an emerging El Nino event. In addition, climate change is expected to continue its warming trends while increasing rainfall extremes including extreme droughts, the report further said.
The study also referenced an initiative Enhancing National Climate Services, which has made climate information easier for Ethiopian health professionals to access and use.
The initiative helps pinpoint which districts will be most exposed to the climatic conditions that foster the spread of malaria and to better target malaria control measures.
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