In October 1993, dengue was first recognized in Jeddah, Saudi Arabia. However, rainfall is inadequate (<60mm/year) to maintain standing water in natural or artificial containers, and a good municipal system makes domestic water storage unnecessary. Dengue surveillance was established in 1994 and detected 37% of cases in construction workers. Other cases appeared to be more common in districts where construction work was common. With a case-control study we estimated the relative importance of construction activities and other potential Aedes aegypti breeding sites to dengue fever in residences.
Methodology
From dengue surveillance we identified 29 persons living in residences in high-incidence districts who had dengue confirmed by virus isolation or anti-dengue IgM. We selected 71 residential controls from persons attending the same reporting clinics and also living in high-incidence districts. We questioned cases and controls about the spatial relationship of their residences to construction activities and to other potential Aedes aegypti breeding sites.
Results
Confirmed dengue was associated with residence near construction work (odds ratio [OR] 7.8; 95% confidence interval [CI] 1.58-52.36). Construction adjacent to a residence (OR = 9.8; 95% CI 1.8-69) or construction directly across the street (OR = 8.7; 95% CI 1.4-67.5) was associated with dengue. However, construction one or more houses away was not (OR = 1.1, 95% CI 0.36-3.38). Dengue cases were also more likely to live near construction block plants (OR=18.3; 95% CI 1.95-431) and construction laborers' camps (OR=8.6, 95% CI 1.18-46.4). Dengue was not associated with other potential Aedes aegypti breeding sites.
Conclusion
The three construction activities associated with residential dengue all have human hosts (laborers) and the vector breeding site (water tanks) in close proximity. The strong association between the residential dengue cases and construction activities imply that much of the dengue transmission in Jeddah may be linked to foci around construction sites. Initially, dengue control measures were applied uniformly in Jeddah, but concentration of these measures at construction sites should be more effective.