Especially in Southeast Asia, for example, rapid population growth and urbanization after World War II has resulted in endemic dengue. An insufficient supply of piped water in this region makes it necessary to store water for drinking and washing; this situation, along with poor sanitation and crowding, helps to create conditions that favor the breeding of Aedes aegypti. Between 1970 and 1987, attack rates of severe DHF in Southeast Asia increased from 15 people per 100,000 population to 170 per 100,000 [11]. In cities like Delhi, the storage of drinking water in pots as well as in open water room coolers provides perfect breeding sites for the disease-carrying mosquitoes [12].
Similarly, in Latin America, rapid urbanization spurred by intensive industrialization and social and economic changes, has led to rapid reinfestation of the mosquito that carries dengue. The Aedes aegypti mosquito was almost eradicated from most Central and South American countries in the 1950s and 1960s as a result of an extensive campaign to end yellow fever, which is carried by the same mosquito. After 1972, however, government complacency and the shift of economic resources to meet the increasing demands imposed by rapid urbanization and inadequate health-care systems dramatically curtailed mosquito control efforts [13][14]. By 1995, Aedes aegypti had returned to the same level of distribution as before the eradication program, and 14 countries in the region reported confirmed cases of DHF [15]. In Mexico, for instance, 358 cases of DHF (with a case fatality rate of 7.8 percent) were confirmed in 1995 compared with only 30 cases in 1994 and only 26 cases between 1984 and 1993 [16] [17].
Tourism and travel have also become important mechanisms for facilitating the dengue virus and its vectors. Aedes albopictus, for instance, was introduced from Asia into the Americas as the result of increased tire trade. Used truck tires in Asia, destined for the United States for recapping, were stored in the open before export, where they collected rainwater and became breeding sites. During the 1980s, more than 1 million tires per year were imported into the United States from Asia of which approximately 20 percent were simply discarded in the environment [18]. In these breeding grounds, the mosquito spread rapidly and has established itself in at least 17 American states [19]. Overall, however, the risk for dengue outbreaks in the United States is small, because most U.S. homes have running water, window and door screens, and air conditioning. In addition, public health surveillance and prevention and control programs tend to be better developed.
Because effective dengue vaccines are not likely to exist for at least 5 to 10 years, the only way to prevent dengue is to eliminate or reduce the mosquito vectors, either by direct control efforts or by improving housing conditions to reduce the number of potential breeding sites. Integrated prevention strategies need to be developed, and high-technology, quick-fix solutions should not be relied upon to combat the virus [20] [21]. (See Improving Health Through Environmental Action.) Without nationwide vector-control programs, however, the absolute number of dengue cases will continue to expand with population growth and the growth of cities [22].
References and notes
11. Donald S. Shepard and Scott B. Halstead, “Dengue (with Notes on Yellow Fever and Japanese Encephalitis),” in Disease Control Priorities in Developing Countries, Dean T. Jamison et al., eds. (Oxford University Press, New York, 1993), p. 304.
12. Tara Patel, “Dengue Fever Outbreak Angers Indian Judges,” New Scientist, Vol. 152, No. 2053 (October 26, 1996), p. 10.
13. Edward B. Hayes and Duane J. Gubler, “Dengue and Dengue Hemorrhagic Fever,” Pediatric Infectious Disease Journal, Vol. 11, No. 4 (1992), p. 315.
14. Op. cit. 1, p. 2398.
15. Op. cit. 7, pp. 55-57.
16. Baltasar Brise
