SEROPREVALENCE OF IgG SPECIFIC FOR DENGUE VIRUS AMONG ADULTS AND CHILDREN IN SANTO DOMINGO, DOMINICAN REPUBLIC TETSU YAMASHIRO, MILDRE DISLA, ANGELA PETIT, DELFIS TAVERAS, MERCEDEZ CASTRO-BELLO, MIGUEL LORA-ORSTE, SONIA VARDEZ, ANA JULIA CESIN, BARBARA GARCIA, AND AKIRA NISHIZONO Institute of Scientific Research, and Department of Infectious Diseases, Faculty of Medicine, Oita University, Oita, Japan; Centro de Educacion Medica de Amistad Dominico-Japonesa, Santo Domingo, Dominican Republic Abstract. The seroprevalence of dengue (DEN) virus-specific IgG was determined by enzyme-linked immunosor- bent assay among 1,008 adults recruited at blood banks and among 201 children less than 10 years old visiting a hospital in Santo Domingo, Dominican Republic. Most (98%, 987 of 1,008) of the adults and 56% (113 of 201) of the children were positive for DEN virus-specific IgG. Among adults, there were no significant differences in the prevalence by age, sex, and residential area of the participants. Among children, the prevalence of DEN virus-specific IgG increased with age (1-2 years old, 0-5%; 3-6 years old, 25-65%; and 7 years old, 76-92%). The prevalence in 50% of those less than one year of age was probably due to maternal antibody transfer. Neutralization tests of adult samples indicate that DEN virus infections with different serotypes have occurred sequentially or simultaneously among the inhabitants of Santo Domingo. INTRODUCTION Dengue (DEN) virus belongs to the genus Flaviviruses, and consists of four serotypes: serotype 1 (DEN-1), serotype 2 (DEN-2), serotype 3 (DEN-3), and serotype 4 (DEN-4). In- fection with DEN virus has been a major concern in DEN- endemic societies for decades worldwide. 1,2 An infection with this virus usually causes self-limiting diseases; fever, rash, and joint pain (dengue fever [DF]). However, a more severe form of DEN virus infection accompanied by hemorrhagic fever (dengue hemorrhagic fever [DHF]) and shock (dengue shock syndrome [DSS]) has occurred in DEN-endemic areas where all four serotypes co-circulate. 3 According to investigations conducted by the World Health Organization, the worldwide incidence of DF is estimated to range from 25 million to 50 million and that of DHF or DSS to be more than 500,000. 4 Dengue virus causes outbreaks and major epidemics in most tropical and subtropical areas, where Aedes aegypti and Ae. albopictus are abundant. These mosquito species are the prin- cipal vectors responsible for the human-to-human transmis- sion and spread of DEN virus infection. 5 Various factors are related to the introduction and spread of DEN virus infection in Santo Domingo, the capital of the Dominican Republic, i.e., increased human transportation by airplane, lack of effective mosquito control, an explosive in- crease in the population, and uncontrolled urbanization, which has resulted in substandard housing and an inadequate water supply, sewage system, and waste management systems for millions of residents. DEN virus infection has been reported to be epidemic in Caribbean countries where Ae. aegypti has infested and un- controlled urbanization has occurred. 6 In the Dominican Re- public, laboratory-confirmed DEN outbreaks, related to epi- demics in the neighboring Caribbean islands, have been re- ported since the 1960s, and each of the four DEN virus serotypes has been attributed as causative. The first appear- ance of each of DEN virus serotype in the Dominican Re- public is as follows: DEN-3 virus in 1963, DEN-4 virus in 1982, DEN-1 virus in 1984, and DEN-2 virus in 1985. 7 In 2000, more than 3,400 cases of DF and DHF caused by each of the four serotypes were reported in the Dominican Republic, with an incidence of 40.75 per 100,000 population (Pan Amer- ican Health Organization, 2000, available at www.paho.org/ english/hcp/hct/vbd/dengue-cases-2000.htm). Exposure to the virus generally occurs in the infantile to juvenile period among residents in DEN-endemic areas, and the prevalence of DEN virus-specific IgG increases with age and reaches its peak before adolescence. 8 Collecting informa- tion on the prevalence of DEN virus-specific IgG among resi- dents of a DEN-endemic area would be an initial step in estimating the magnitude of DEN virus infection in a popu- lation. In the present study, the prevalence of IgG specific for DEN virus was surveyed and determined among residents of Santo Domingo who visited blood banks for blood donation, and among hospital-visiting children, to estimate the magni- tude of DEN virus circulation in this city and the age at which residents of Santo Domingo become initially exposed to DEN virus. Serotypes of DEN virus circulating among the residents of Santo Domingo were also determined by focus reduction neutralization tests. MATERIALS AND METHODS Sample collection from adults. All adult samples were col- lected at seven blood banks of public hospitals located in Santo Domingo from June 17 to July 23, 2002. Study subjects were restricted to volunteers who resided in the Santo Dom- ingo district (Distrito Nacional). One to two milliliters of blood was collected from an inlet tube connecting the needle to a blood reservoir bag prior to screening for infectious agents (hepatitis B virus, hepatitis C virus, human immuno- deficiency virus, syphilis, human T cell lymphotropic virus 1), as well as for detection of elevated levels of transaminases. Basic epidemiologic information such as age, sex, and current residential area was also collected. Sample collection from children. Blood samples were col- lected from children 10 years old visiting the outpatient department of Centro de Gastroenterologı´a Hospital in Santo Domingo from July 30 to August 27, 2002. Study subjects generally visited the hospital seeking care for gastrointestinal diseases. Patients with fever were carefully excluded by mea- suring their axillary temperature to minimize the number of patients with acute DEN virus infections, which would aug- ment the prevalence of DEN virus-specific IgG among the Am. J. Trop. Med. Hyg., 71(2), 2004, pp. 138–143 Copyright © 2004 by The American Society of Tropical Medicine and Hygiene 138