This study is conducted at the Health Center Sócrates Flores Vivas (HCSFV) in District II of Managua, the capital of Nicaragua. District II is adjacent to Lake Managua, and the Health Center serves a population of approximately 60,047. The primary health-care facility is the HCSFV; study children requiring additional medical attention are transferred to the study hospital, the National Pediatric Reference Hospital, Hospital Infantil Manuel de Jesús Rivera (HIMJR). Clinical laboratory tests are performed in the HCSFV, while all virologic and serologic tests are performed at the National Virology Laboratory of the Centro Nacional de Diagnóstico y Referencia. All study facilities are part of the Nicaraguan Ministry of Health, and the national directors of epidemiology, the reference laboratories, and the health province of Managua sit on the Executive Committee of the Pediatric Dengue Cohort Study. A formal agreement (“convenio”) supporting the study is signed by the Minister of Health and the principal investigator of the study. Ninety-five percent of study personnel are Nicaraguan, and all decisions are made by consensus by a technical committee composed of Pediatric Dengue Cohort Study site directors, informatics and quality control directors, the study coordinator, and the principal investigator. This study was approved by the institutional review boards at the University of California, Berkeley, the International Vaccine Initiative, and the Nicaraguan Ministry of Health (Centro Nacional de Diagnóstico y Referencia and HIMJR).