A hemorrhagic fever is a viral infection that features a high fever and a high volume of (copious) bleeding. The bleeding is caused by the formation of tiny blood clots throughout the bloodstream. These blood clots--also called microthrombi--deplete platelets and fibrinogen in the bloodstream. When bleeding begins, the factors needed for the clotting of the blood are scarce. Thus, uncontrolled bleeding (hemorrhage) ensues.

Several tropical fevers fall into this category. These include Dengue hemorrhagic fever (caused by the Dengue virus), Korean hemorrhagic fever (caused by the Hantaan virus), Lassa fever (caused by the Lassa virus), Marburg fever (caused by the Marburg virus), Rift Valley fever (caused by the Rift Valley fever virus) and Ebola fever (caused by the Ebola virus). There is no cure for these infections. Treatment consists of keeping the patient as comfortable and infused with blood and fluids as...