ABSTRACT
Guides for Emergency Response: Biological Agent or Weapon: Viral Hemorrhagic Fevers (VHFs) Viral Hemorrhagic Fevers (VHF): Viral hemorrhagic fevers (VHFs), including Crimean-Congo fever, Rift Valley fever, Lassa fever, Ebola fever, and others, are a diverse group of human viral illnesses characterized by acute febrile onset accompanied by headache and complicated by increased vascular permeability, damage, and bleeding; mortality is high. Viral pathogenesis is complex, incompletely understood and varies among specifi c viruses. Some infections result in immune complex deposition that activates complement and other infl ammatory results. Such a process damages vascular endothelium, results in capillary leak, and deregulates vascular smooth muscle tone. Th ey lead to hypotension, shock, and end-organ failures. Some of these diseases activate coagulation cascades and result in disseminated intravascular coagulation (DIC). Hemorrhage can also be enhanced by specifi c end-organ failures. As an example, yellow fever can cause massive hepatic (relating to, aff ecting, or associated with the liver) necrosis resulting in a defi ciency of vitamin K-dependent clotting factors. Th e uremia complicating the acute renal failure of the hemorrhagic fever syndrome (HFRS) leads to platelet dysfunction, further promoting hemorrhage. Th e end result is that viral hemorrhagic fever is highly contagious, but some VHF viruses can cause relatively mild illnesses, while many others can cause severe, lifethreatening disease. With a few exceptions, there is no cure or an established drug treatment for viral hemorrhagic fevers.
