265 Am. J. Trop. Med. Hyg., 59(2), 1998, pp. 265–271 Copyright  1998 by The American Society of Tropical Medicine and Hygiene USING DISABILITY-ADJUSTED LIFE YEARS TO ASSESS THE ECONOMIC IMPACT OF DENGUE IN PUERTO RICO: 1984–1994 MARTIN I. MELTZER, JOSE ´ G. RIGAU-PE ´ REZ, GARY G. CLARK, PAUL REITER, AND DUANE J. GUBLER National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Dengue Branch, Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, San Juan, Puerto Rico; Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado Abstract. This study presents the disability-adjusted life years (DALYs), a non-monetary economic measure of impact, lost to dengue in Puerto Rico for the period 1984–1994. Data on the number of reported cases, cases with hemorrhagic manifestations, hospitalizations, and deaths were obtained from a surveillance system maintained at the Dengue Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention (San Juan, PR). The reported cases were divided into two age groups (0–15 years old and 15 years old), and then multiplied by predetermined factors (10 for 0–15 years; 27 for 15 years) to allow for age-related under-reporting of cases. Severity of dengue was modeled by classifying cases into three groups: dengue fever, dengue with severe manifes- tations, and hospitalized cases. Each group was assigned a different number of days lost because of dengue-related disability. Dengue caused an average of 658 DALYs per year per million population (SE = 114, range = 145–1,519). A multivariate sensitivity analysis, which simultaneously altered the values of six input variables, produced a mean of 580 DALYs/year/million population, with a maximum average of 1,021 DALYs/year/million population, and a maximum, single-year estimate for 1994 of 2,153 DALYs/million population. The most important input was the number of days lost to classic dengue. The DALYs/year/million population lost to dengue in Puerto Rico are much greater than previous estimates concerning the impact of dengue hemorrhagic fever alone. The loss to dengue is similar to the losses per million population in the Latin American and Caribbean region attributed to any of the following diseases or disease clusters; the childhood cluster (polio, measles, pertussis, diphtheria, tetanus), meningitis, hepatitis, or malaria. The loss is also of the same order of magnitude as any one of the following: tuberculosis, sexually transmitted diseases (excluding human immunodeficiency virus), tropical cluster (e.g., Chagas’ disease, leish- maniasis), or intestinal helminths. The results objectively suggest that when governments and international funding agencies allocate resources for research and control, dengue should be given a priority equal to many other infectious diseases that are generally considered more important. Dengue fever is caused by a mosquito-borne virus, which has four serotypes. 1, 2 The disease has a wide range of clin- ical manifestations. A patient with classic dengue fever will typically experience fever, headache, pain in the muscles, joints and bones, nausea, and vomiting and develop a rash. 3, 4 Although most dengue infections can be characterized as mild, 2, 5 some cases will present as dengue hemorrhagic fever (DHF). The latter is characterized by hemorrhagic manifes- tations and excessive capillary permeability. Approximately 33% of patients with DHF will experience serious circula- tory failure, known as dengue shock syndrome (DSS). 3 The fatality rate for those patients with DSS can be between 12% and 44%, 5 although infusions of fluids, electrolyte manage- ment, and use of oxygen can reduce the fatality rate to less than 1%. 3 Cases of dengue fever were described more than 200 years ago, 2 and histories of dengue and dengue epidemics have been written. 2, 3, 6–10 After the Second World War, populations of the most important mosquito vector, Aedes aegypti, were suppressed in Latin America. The control campaigns, how- ever, were abandoned in the early 1970s and the vector re- established itself in virtually all of the countries that had vector control campaigns as well as expanding into a few new areas, such as the Amazon basin. This re-establishment and expansion of the vector has resulted in the dengue vi- ruses spreading rapidly around the globe. In 1980, it was estimated that at least 1.5 billion people live in areas with dengue activity. 10 In 1995, this estimate was increased to 2.5 billion, 11 as residents in several additional countries became newly infected with dengue. Most of these newly infected countries are in Africa, South and Central America, and the Caribbean. 11 The number of cases have led researchers to describe the incidence of dengue and DHF as pandemic. 6–8, 10 Illustrating the rate of increase is the fact that globally, there were 25,000–30,000 reported cases of DHF per year from 1956 to 1980. For the period 1981–1985, an average of 137,504 cases of DHF/DSS per year were reported, and for 1986–1990, the average number of reported DHF/DSS cases per year increased to 267,692. 12 Given problems of diagnosis and reporting, it is likely that these figures are conservatively low. It has been estimated that there were more than 1.3 million cases of DHF in the period 1986–1990. 12 The reasons for the geographic spread and increased incidence of dengue and DHF have been described, 2, 6, 8, 11, 13–15 and include an in- crease in international trade, rapid urbanization without con- current improvements in sanitation, and a decrease in the effective control of the vectors. The rapid spread of dengue and DHF and the large numbers of people afflicted have resulted in dengue being classified by national and interna- tional public health authorities as an emerging, or re-emerg- ing, infectious disease. 8, 11, 16, 17 Curiously, despite the large number of victims, there are few estimates of the economic impact of dengue. Estimates of the total direct and indirect costs from the 1977 epidemic in Puerto Rico range from US $6.1 million to $15.6 million (approximately $26–$31 per clinically ill case). 18 The 1981 epidemic in Cuba, which had a total of 344,203 reported cases, cost about US $103 million (approximately $299 per reported case). 19 An outbreak in 1980 in Thailand was esti- mated to cost a minimum of US $6.8 million (approximately