Patient description: An 18-year-old male returning from a recent vacation in Asia presents to the ER with a sudden onset of high fever, chills, facial flushing, epistaxis and severe headache and joint pain. His complete blood count reveals leukopenia, increased hematocrit concentration and thrombocytopenia.

Clinical trial eligibility criteria: eligible ages (years): 18.0-45.0,  Dengue Male or female at least 18 and less than or equal to 45 years old at time of screening In good health as determined by medical history, physical examination including height and weight, and clinical safety laboratory examinations. For creatinine and alkaline phosphatase levels the applicable cut-offs for determination are the upper limits of normal only, as there is no clinical significance associated with results below the lower limits of normal for these laboratory values. For aspartate aminotransferase (AST) and alanine aminotransferase (ALT), the applicable cut-offs for determination are less than 1.5 times the upper limits of normal, as there is no clinical significance associated with results below the lower limits of normal for these laboratory values or with mild elevations above the upper limits of normal Laboratory values not listed in Table 3 which are obtained as part of a reference laboratory pre-determined panel will be considered as acceptable for enrollment if they are either within reference laboratory normal range or within the ranges specified for a grade I AE per the protocol Toxicology Tables in Appendix B. Values within reference laboratory normal ranges or within ranges specified for a grade I AE per the Toxicology Tables in Appendix B will be considered as discussed with the medical monitor and may be enrolled with no further discussion. Values with deviations outside the ranges specified for a grade 1 AE in the Toxciology Tables in Appendix B will be discussed further between the PI and the medical monitor prior to vaccination and assessed for impact on volunteer safety. Urinalyses obtained from female volunteers on their menses may be repeated after their menses have concluded without discussion with the medical monitor. Laboratory values which are not listed in the Toxicology Tables in Appendix B and which are out of the reference laboratory normal range will be discussed with the DMID medical monitor to determine its relevance for safety and impact on enrollment and follow-up vaccinations Blood tests negative for antibodies to human immunodeficiency virus (HIV)-1, Hepatitis C, dengue, West Nile, and negative for Hepatitis B surface antigen No history of dengue or West Nile infection or participation in a previous dengue or West Nile vaccine trial Females of child bearing potential must have a negative urine pregnancy test result during screening and a negative urine pregnancy test immediately prior to vaccination and be willing to use oral, implantable, transdermal or injectable contraceptives or another reliable means of contraception approved by the Investigator (intrauterine device, female condom, diaphragm with spermicidal, cervical cap, use of condom by the sexual partner or a sterile sexual partner, or abstinence) from screening until after the last blood sample (at day 270) Willing and able to give written informed consent to participate Willing and able to communicate with the investigator and understand the requirements of the study Electrocardiogram (ECG) in absence of clinical significance (e.g., complete left or right bundle branch block, incomplete left bundle branch block or sustained ventricular arrhythmia, or two premature ventricular contraction's (PVC's) in a row, or ST elevation consistent with ischemia) Weight: greater than or equal to 110 lb  Any condition which would limit the subject's ability to complete the study in the opinion of the Investigator Clinically significant hematological, renal, hepatic, pulmonary, central nervous, cardiovascular, thromboembolic, autoimmune, coagulopathic, or gastrointestinal disorders or history of such disorders Any history of malignancy with the exception of basal cell carcinoma Previous history , or current diagnosis of diabetes mellitus Pulse >95 or <40 at rest or irregular, systolic blood pressure (bp) >170 or <90 at rest or diastolic bp >90 or <50 at rest, body temperature >100 F, respirations >25 per minute at rest History of allergy to penicillin, neomycin, streptomycin or gentamicin History of hypersensitivity to any vaccine History of previous vaccination with Yellow Fever (YF) vaccine or Japanese Encephalitis (JE) vaccine or planned receipt of either YF or JE vaccine during the course of the study Previous history of infection with dengue or West Nile or seropositive antibody status to dengue or West Nile virus or participation in a vaccine trial for either of these Travel or planned travel to a dengue-endemic area including the Caribbean, Mexico, Central America, South America or Asia during the study period or in the month prior to screening. An updated map of dengue endemic areas is available at the CDC Yellow Book 2010 website (http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-5/dengue-fever-dengue-hemorrhagic-fever.aspx) and a list of dengue endemic countries is provided in the Manual of Procedures (MOP)