The emergence of epidemic dengue fever and dengue hemorrhagic fever in the Americas: a case of failed public health policy.

began in Southeast Asia during World War II and in the years following that conflict (1). In the last 25 years of the 20th century the pandemic intensified, with increased geographic spread of both the viruses and the principal mosquito vector, Aedes aegypti. This led to larger and more frequent epidemics and to the emergence of DHF as tropical countries and regions became hyperendemic with the co-circulation of multiple virus serotypes. With the exception of sporadic epidemics in the Caribbean islands, dengue and yellow fever were effectively controlled in the Americas from 1946 until the late 1970s as a result of the Ae. aegypti eradication program conducted by the Pan American Health Organization (PAHO) (1, 2). This was a vertically structured, paramilitary program that focused on mosquito larval control using source reduction and use of insecticides, primarily dichlorodiphenyltrichloroethane (DDT). This highly successful program, however, was disbanded in the early 1970s because there was no longer a perceived need and there were competing priorities for resources; control of dengue and yellow fever was thereafter merged with malaria control. Another major policy change at that time was the use of ultra-low-volume space sprays for killing adult mosquitoes (adulticides) as the recommended method to control Ae. aegypti and thus prevent and control DF and DHF. Both of these decisions were major policy failures because they were ineffective in preventing the re-emergence of epidemic DF and the emergence of DHF in the Region. During the 1970s and 1980s, Ae. aegypti re-infested all of the countries from which it had been eliminated (3). Generally, within a few years of reinfestation a country experienced epidemic DF, followed by the emergence of DHF as the countries became hyperendemic. Alarms about this trend were sounded (3–8), and two international health agencies, the United States Centers for Disease Control and Prevention (CDC) and PAHO, responded by working together to develop laboratory-based surveillance activities and programs for prevention and control (3, 7, 9). A major focus of these activities was in Puerto Rico, where the CDC had established a laboratory devoted to surveillance, prevention, and control of DF and DHF (3). This group, in collaboration with the Puerto Rico Health Department (PRHD) and PAHO, sponsored the First International Seminar on Dengue Hemorrhagic Fever in the Americas in June 1985, to highlight the importance of this disease and the increasing threat it posed to the Region (7). This group also developed a new strategy for the prevention and control of epidemic DF and DHF, with five basic components: (1) Active, laboratory-based surveillance, (2) emergency preparedness and response for mosquito control, (3) emergency hospitalization and treatment of DHF patients, (4) education of the medical community on the clinical diagnosis and management of DHF, and (5) integrated, community-based Ae. aegypti control (3, 10). It was this plan that gave rise to PAHO’s Guidelines for prevention and control of DHF (9) and to the current World Health Organization’s Global Strategy for the Prevention and Control of Dengue Fever and Dengue Haemorrhagic Fever (11). PAHO was proactive in encouraging and helping its Member States develop prevention and control plans for DF and DHF through the 1980s and 1990s, and most countries responded by developing such plans. In 1993, the CDC Editorial