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.
Craig
M H
MH
Malaria Research Programme, Medical Research Council, Durban, South Africa. craigm@mrc.ac.za
Kleinschmidt
I
I
Le Sueur
D
D
Sharp
B L
BL
D000383:Agriculture / Q000639:trends; D002980:Climate; D004196:Disease Outbreaks; D004351:Drug Resistance; D004641:Emigration and Immigration / Q000706:statistics & numerical data; D015658:HIV Infections / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007305:Insecticide Resistance; D016014:Linear Models; D008288:Malaria / Q000453:epidemiology* / Q000209:etiology / Q000635:transmission; D012307:Risk Factors; D012621:Seasons; D013019:South Africa / Q000453:epidemiology