Seasonally lagged effects of climatic factors on malaria incidence in South Africa

Takayoshi Ikeda,Yushi Morioka,Swadhin K Behera,Masahiro Hashizume,Philip Kruger,Rajendra Maharaj,Noboru Minakawa,Ataru Tsuzuki

doi:10.1038/s41598-017-02680-6

Abstract

Globally, malaria cases have drastically dropped in recent years. However, a high incidence of malaria remains in some sub-Saharan African countries. South Africa is mostly malaria-free, but northeastern provinces continue to experience seasonal outbreaks. Here we investigate the association between malaria incidence and spatio-temporal climate variations in Limpopo. First, dominant spatial patterns in malaria incidence anomalies were identified using self-organizing maps. Composite analysis found significant associations among incidence anomalies and climate patterns. A high incidence of malaria during the pre-peak season (Sep-Nov) was associated with the climate phenomenon La Niña and cool air temperatures over southern Africa. There was also high precipitation over neighbouring countries two to six months prior to malaria incidence. During the peak season (Dec-Feb), high incidence was associated with positive phase of Indian Ocean Subtropical Dipole. Warm temperatures and high precipitation in neighbouring countries were also observed two months prior to increased malaria incidence. This lagged association between regional climate and malaria incidence suggests that in areas at high risk for malaria, such as Limpopo, management plans should consider not only local climate patterns but those of neighbouring countries as well. These findings highlight the need to strengthen cross-border control of malaria to minimize its spread.

Highlights

Malaria is the deadliest vector-borne disease affecting people worldwide, with nearly half of the world’s population at risk
To test whether malaria incidence rate anomalies were associated with local and regional climate factors, and large-scale climate phenomena, we first investigated the relationship among monthly malaria incidence of Limpopo and temperature, precipitation, and sea surface temperature (SST) anomalies
Positive correlation is shown between precipitation and malaria incidence rate (MIR) anomalies over southern Mozambique at three-month lag (Fig. 3a)

Summary

Introduction

Malaria is the deadliest vector-borne disease affecting people worldwide, with nearly half of the world’s population at risk. The annual malaria incidence link to sea surface temperature (SST) associated with climate variation has been described previously[4] and malaria incidence has been linked to remote influences such as the monsoon rainfalls[5] and large-scale climate phenomena, such as the Indian Ocean Dipole[6,7,8] and El Niño-Southern Oscillation[9, 10]. These studies suggest that remote large-scale climate phenomena could influence local malaria incidence via atmospheric teleconnection. Previous studies have reported relationships between malaria and climate variables including rainfall, humidity and temperature for African[15,16,17,18,19,20,21,22] and Asian countries[23,24,25]

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Results

Conclusion