Comments on the epidemiology, pathogenesis and control of dengue

Dengue is currently the most important viral disease transmitted to man by arthropods, whether measured by the number of cases or number of deaths. Prevalence of the disease is highest in tropical Asia, intermediate in tropical America, and lowest in tropical Africa. Four distinct dengue viruses have been identified. Types 2 and 3 appear to be more pathogenic on the average than types 1 and 4, but all four can cause severe or fatal dengue syndromes. Infection with any of the four viruses confers life-long homotypic, but not heterotypic, immunity. Dengue viruses can be transmitted by several mosquito species of the genus Aedes, but by far the most common vector is Aedes aegypti. All non-human primates that have been tested are susceptible to infection, but none exhibit signs of illness. The resulting lack of a suitable experimental host other than man has slowed progress in understanding the pathogenesis of severe forms of the disease. Controversy continues over the hypothesis that a first dengue infection increases the risk of severe disease upon re-infection as well as over the principal sites of replication. With regard to replication sites, some authors have mentioned cells of the mononuclear phagocyte lineage while others have implicated hepatocytes. No vaccine is currently available for dengue. Because the principal mosquito vector can use a wide variety of small domestic containers, vector control programs have not been highly effective.