Viral hemorrhagic fevers (VHFs) are illnesses caused by several types of viruses. Some of these viruses cause mild illness. Many others lead to life-threatening diseases with no known cures. One of the best known of this group is the Ebola virus.
Viral hemorrhagic fevers are rare in the U.S. They generally occur in Africa, South American, and Asia. However, health officials are concerned that these viruses could be used in biological terrorism