Predictive Indicators for Forecasting Epidemic of Dengue/Dengue Haemorrhagic Fever Through Epidemiological, Virological and Entomological Surveillance

Dengue/dengue haemorrhagic fever is the leading cause of death from the declared infectious diseases in children in southern Vietnam. The dengue epidemic in 1998 was an extensive one, with the morbidity rate of 455 cases/100 000 pop. and mortality rate of 1.27/100 000 pop. DEN-3 was the predominant serotype. However, in 1999, there was a lower morbidity (80.7 cases/100 000) and a lower mortality (0.23 deaths/100 000). The circulation of DEN-3 virus decreased and that of DEN-4 virus emerged. In both the years, most of the cases and deaths occurred in children under 15 years of age. Shock accounted for 15.3% and 13.5%, respectively, of all DF/DHF cases in 1998 and 1999, of which 2.5% and 2.1% died. The epidemic curve reached its peak in the rainy season (June to October). An excessive increase in the number of cases compared with the average of the previous five years and an increased circulation of a new dengue virus serotype during the first quarter may be used as indicators to predict larger epidemics in the year. There was no correlation of entomological indices with the epidemiological situation in this study.