The yearly return of dengue

As certainly as the rainy season arrives each year, El Salvador is facing the return of thousands of cases of dengue fever. El Diario de Hoy reports that the number of suspected cases of dengue fever in the country is 3000 and rising. Dengue is a virus transmitted the bite of the Aedes aegypti mosquito. Most cases produce fever and other nonfatal symptoms, but a small percentage of cases produce dengue hemorrhagic fever which is sometimes fatal.

The US Centers for Disease Control points to various factors which have led to dengue becoming a major public health problem in the Americas, including:
Uncontrolled urbanization and concurrent population growth ... have resulted in substandard housing and inadequate water, sewer, and waste management systems, all of which increase Ae. aegypti population densities and facilitate transmission of Ae. aegypti-borne disease....

Lastly, in most countries the public health infrastructure has deteriorated. Limited financial and human resources and competing priorities have resulted in a "crisis mentality" with emphasis on implementing so-called emergency control methods in response to epidemics rather than on developing programs to prevent epidemic transmission.
El Salvador combats dengue with mosquito control spraying and public education campaigns to emphasize the importance of eliminating standing water and covering water barrels or other locations where the insect can breed.