Exploring 30 years of malaria case data in KwaZulu‐Natal, South Africa: Part II. The impact of non‐climatic factors

Malaria transmission is a multifactorial phenomenon. Climate is a major limiting factor in the spatial and temporal distribution of malaria, but many non‐climatic factors may alter or override the effect of climate. Thirty years of monthly malaria incidence data from KwaZulu‐Natal province, South Africa, reveal strong medium and long‐term trends, which were not present in the climate data. This paper explores various non‐climatic factors that may have contributed towards the observed trends. The development of antimalarial drug resistance, available information on human immunodeficiency virus (HIV) prevalence, cross‐border people movements, agricultural activities, emergence of insecticide resistance and the case reporting system are reviewed and their potential effect on malaria transmission examined. Single‐variable linear regression analysis showed significant association between seasonal case totals (log‐transformed) and the measured level of drug resistance (log‐transformed) (r2 = 0.558, n = 10, P = 0.013) as well as relative measures of HIV infection since 1990 (r2 = 0.846, n = 11, P = 0.001). The other factors appear to have affected the level of malaria transmission at certain periods and to some degree. The importance of surveillance and inclusion of non‐climatic variables in analysis of malaria data is demonstrated.

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