Our hypothesis is that the presence of gallbladder wall thickening and/or pleural effusions in children correlates with progression to Dengue hemorrhagic fever and Dengue shock. In addition, we hypothesize that sonographic imaging of pediatric patients presenting to the emergency department with a fever during a Dengue fever outbreak will change management and disposition. Our specific aim is to 1) compare the accuracy of bedside ultrasound detection of intra-thoracic fluid, peritoneal free fluid, and gallbladder wall thickening and physical exam versus physical exam alone in diagnosing dengue fever and 2) determine the association between sonographic features of dengue (intra-thoracic fluid and gallbladder wall thickening) and clinical outcome in children with dengue fever.