Hemorrhagic Fever

Hemorrhagic fevers (HFs) are diseases characterized by raised body temperature (fever) and rapid blood loss (hemorrhage), which may be either internal or external. They are often referred to as viral hemorrhagic fevers (VHFs) because most are caused by a virus from one of four families: Filoviridae, Arenaviridae, Bunyaviridae, or Flaviviridae. Well-known HFs include Ebola HF, Marpurg HF, Lassa fever, and Rift Valley fever.

VHFs are zoonotic and reside in an animal reservoir host or arthropod. Because VHFs are dependent on their animal or insect hosts, outbreaks are generally restricted to areas where the hosts live; this is why many VHFs include a geographic designation in their name. This risk of VHFs, therefore, varies by location: Carriers of some diseases exist in very limited geographic areas, and the risk of contracting those VHF is also limited to those areas.

However, other carriers (such as the common rat) exist throughout the world, and thus some VHFs themselves are widely distributed. In addition, VHFs may be spread through transportation of infected animals (Marpurg virus was introduced to Germany and Yugoslavia by infected lab monkeys, for instance) and some, including Ebola, Marpurg, Lassa, and Crimean-Congo Fevers, can also be transmitted from an infected human to another human, or through contact with the blood or other body fluids of an infected person.

Signs and symptoms common to VHFs include fever, fatigue, dizziness, muscle aches, and weakness and exhaustion. There may be signs of bleeding under the skin or from body orifices, and severe cases may show shock, coma, or seizures. Some VHFs cause only mild illness, while others can be life threatening. Renal failure is associated with some VHFs, and Ebola HF is believed to be fatal in 50 to 90 percent of clinically ill cases, for instance. There is no cure for most VHFs, and no treatment other than supportive care; exceptions include Ribavarin, which has been used to treat Lassa fever, and convalescent-phase plasma, which has been used to treat Argentine HF.