Viral hemorrhagic fevers (VHFs) are a group of diseases that are caused by several distinct families of viruses. The term “viral hemorrhagic fever” refers to a condition that affects many organ systems of the body, damages the overall cardiovascular system, and reduces the body’s ability to function on its own. Symptoms of this type of condition can vary but often include bleeding, or hemorrhaging. Some VHFs cause relatively mild illness, while others can cause severe, life threatening disease. Most VHFs have no known cure or vaccine. Although VHFs are caused by several families of viruses, these viruses share some common characteristics:
They are RNA viruses, meaning viruses that have ribonucleic acid (RNA) as their genetic material. These viruses are the most common cause of emerging disease in people because RNA viruses change over time at a high rate. They are covered, or enveloped, in a lipoprotein outer layer, making it easier to destroy these viruses with physical (heat, sunlight, gamma rays) and chemical (bleach, detergents, solvents) methods. They naturally exist in animal or insect populations, referred to as host populations, and are generally restricted to the geographical areas where the host species live. They spread to people when a person encounters an infected animal or insect host. After the initial spread into the human population, some VHF viruses can continue to spread from person-to-person. Outbreaks of VHFs in people can be difficult to prevent since they can occur sporadically and cannot be easily predicted. VHF diseases by
