Indicators for the forecasting of malaria epidemics.

The entomological inoculation rate is presented as a comprehensive indicator of malaria transmission level, its relative changes reflecting the risk of potential epidemic development. This rate is a known function of several epidemiological direct factors and is particularly sensitive to the survival rate and the sporogonic cycle of the vector. Although not yet fully quantifiable, relationships exist between direct factors responsible for the transmission of infection and certain meteorological and environmental indirect factors like air temperature, relative humidity, or importation of malaria parasites.The establishment of a two-stage monitoring system is suggested: the first stage would involve setting up a warning system based on the surveillance of the relevant indirect factors; at the appropriate time, this would trigger the second stage monitoring of the epidemiological direct factors having a definite bearing on the development of malaria outbreaks. It is recognized that the gain in reliability of the proposed approach depends largely on the progress still to be achieved in the quantification of the complex system of relations connecting the main direct factors with single or combined indirect factors. It is also noted that the proposed monitoring system should, in due course, provide the decision-makers with the epidemiological information required for the selection and implementation of intervention measures designed to prevent epidemic resurgences.