Dengue, a viral hemorrhagic fever (VHF) virus, is the most common mosquito-borne illness (Figs. 1 and 2), and one of the fastest spreading infections worldwide. It is a significant global health concern given there are estimated 3 billion people who live in areas where dengue virus can be transmitted. Some suggest nearly half of the entire global population is at risk, including parts of the United States. Viral hemorrhagic fevers (VHFs) refer to a group of infectious illnesses that are caused by several distinct families of viruses, not surprisingly called the viral hemorrhagic fever viruses that include Ebola, Lassa, dengue, and others. VHFs are distributed worldwide. VHFs are a taxonomically diverse group of viruses capable of causing high morbidity and mortality. In addition to endemic illness worldwide, VHFs remain of considerable interest as possible biological weapons. Regardless of the pathogen, VHF refers to a severe multisystem syndrome that results primarily in fevers and bleeding risks. Some form of hematological event secondary to microvascular damage and changes in vascular permeability can occur, along with other symptoms. Inherent with VHFs, the overall vascular system is affected, resulting at times in severe dysregulation of coagulation; depending upon the underlying viral illness, a variety in severity of bleeding can occur from petechiae to circulatory collapse. Some VHF viruses cause primarily relatively mild illnesses, others cause a broad range (dengue), and yet others result in life-threatening disease (Ebola). Most VHFs are considered biosafety level 4 (BSL-4) pathogens—the highest level of security and threat, usually associated with pathogens for which there is no treatment and/or preventive measure. Exceptions to BSL-4 are dengue and yellow fever. VHF viruses belong to four distinct families (Table 1): arenaviruses, filoviruses, bunyaviruses, and flaviviruses that share the following common features: