CYCLES OF MALARIA ASSOCIATED WITH EL-NINO IN VENEZUELA

Context.-Malaria has been increasing globally, and epidemics tend to o ccur when weather conditions favor this vector-borne disease, Long-ter m meteorologic forecasting using El Nino Southern Oscillation (ENSO) m ay assist in anticipating epidemics and targeting scarce resources. Ob jective.-To determine whether malaria epidemics in Venezuela are relat ed to ENSO and rainfall and to determine whether such a relationship c ould be used to predict outbreaks. Design.-Retrospective analysis oi n ational malaria morbidity (1975-1995) and mortality (1910-1935) data i n the coastal zone and interior of Venezuela in relation to El Nino ev ents and rainfall. Main Outcome Measure.-Correlation between malaria m ortality and morbidity and sea surface temperatures (SSTs) in the East ern Tropical Pacific, a parameter of ENSO. Results.-Malaria mortality and morbidity have increased by an average of 36.5% (95% confidence in terval, 3.7%-69.3%; P=.004) in years following recognized El Nino even ts, A moderate correlation was found between Pacific tropical SST duri ng a Nino event and malaria 1 year later (r=0.50, P<.001). Malaria mor tality is more strongly related to drought in the year preceding outbr eaks than to rainfall during epidemic years. Conclusions.-Historic and recent data from Venezuela demonstrate that malaria increases by an a verage of about one third in the year following a Nino event; change i n malaria risk can be predicted from Pacific SSTs in the previous year , Therefore, the occurrence of an EI Nino event may help predict malar ia epidemics in this part of South America.