Environmental factors and incidence of dengue fever and dengue haemorrhagic fever in an urban area, Southern Thailand

Using the enumeration district (ED) block level this study looked at the incidence of dengue fever and dengue haemorrhagic fever (DF/DHF) within the Songkhla municipality in Thailand. Each of the 146 blocks in this area were considered as study units and surveyed for their environmental characteristics. A total of 287 cases of DH/DHF occurring in the year 1998 were selected for this study and the location of their homes mapped. Clustering analysis showed point clustering of the homes (P < 0.0001) which was probably due to high density habitation, without any actual prevalence of case clustering. There was no evidence of clustering of the ED blocks with an incidence of DF/DHF (P = 0.32). DF/DHF incidence for each block was strongly associated with the percentages of shop-houses, brick-made houses and houses with poor garbage disposal (all P < 0.01). DF/DHF control should be emphasized for the areas which have a predominance of these housing types.