Viral hemorrhagic fevers (VHFs) refer to a group of illnesses that are caused by several distinct families of viruses. In general, the term "viral hemorrhagic fever" is used to describe a severe multisystem syndrome, as many different organs and systems in the body are affected. Characteristically, the overall vascular system is damaged, and the body's ability to regulate itself is impaired. These symptoms are often accompanied by hemorrhage
(severe bleeding), which is why this group of illnesses is called hemorrhagic fevers.
However, the bleeding itself is rarely life-threatening. While some types of hemorrhagic fever viruses can cause relatively mild illnesses, many of these viruses, such as Ebola and
Marburg, cause severe, life-threatening disease.
The Centers for Disease Control and Prevention identifies hemorrhagic fever viruses as agents that could be used as biological weapons because some are highly infectious, can be easily spread through the air, and have the potential to cause great numbers of illnesses and deaths. They are also known to have been the subject of biological weapons research.
Most viruses causing hemorrhagic fever are zoonotic, which means they are initially transmitted to humans by animal or insect reservoir hosts. The viruses carried in rodent reservoirs are transmitted when humans have contact with urine, fecal matter, saliva, or other body excretions from the infected rodents, or when humans have contact with the bodies of infected animals, either dead or alive. The viruses associated with arthropod vectors are spread most often when the vector mosquito or tick bites a human, or when a human crushes a tick. However, some of these vectors may spread virus to animals, such as livestock. Humans then become infected when they care for or slaughter the animals.
Occasionally, an infected traveler may become infected in an area where the virus occurs naturally, and then travel to another area where the virus is not normally found. If the virus is a type that can be transmitted by person-to-person contact, the traveler can infect other people. Ebola, Marburg, Lassa and Crimean-Congo hemorrhagic fever viruses are examples. This type of secondary transmission of the virus can occur through direct contact with infected people or their body fluids. It can also occur indirectly, through contact with objects contaminated with infected body fluids, such as bedding used by a sick person, or contaminated syringes and needles.
Humans can contract viral hemorrhagic fever during a bioterrorist attack in which a VHF is weaponized.

Specific signs and symptoms vary by the type of VHF, but initial signs and symptoms often include marked fever, dizziness, rashes, muscle aches, loss of strength, headache, and fatigue. Patients with severe cases of VHF often show signs of bleeding under the skin, in internal organs, or from body orifices like the mouth, eyes, or ears. However, although they may bleed from many sites around the body, patients rarely die because of blood loss.
Severely ill patient cases may also show shock, nervous system malfunction, coma, delirium, and seizures. Some types of VHF are associated with renal (kidney) failure.
After an incubation period of 1-3 weeks, illness begins insidiously, with early symptoms of fever, sore throat, weakness, and malaise. Typically, symptoms develop within days but may not appear until several weeks after exposure.
Patients receive supportive therapy, but generally speaking, there is no other treatment or established cure for VHFs. Ribavirin, an antiviral drug, has been effective in treating some individuals with Lassa fever or hemorrhagic fever with renal syndrome. The only licensed, approved vaccines for VHFs are for yellow fever and Argentine hemorrhagic fever. To be successful in preventing the disease, the vaccine must be received prior to exposure.
Experimental vaccines for several other VHFs are being studied, but are not yet licensed or approved for general use.
With the exception of yellow fever and Argentine hemorrhagic fever, for which vaccines have been developed, no vaccines exist that can protect against these diseases. Therefore, prevention efforts must concentrate on avoiding contact with host species. If prevention methods fail and a case of VHF does occur, efforts should focus on preventing further transmission from person to person, if the virus can be transmitted in this way.
For those hemorrhagic fever viruses that can be transmitted from one person to another, avoiding close physical contact with infected people and their body fluids is the most important way of controlling the spread of disease. Infection control techniques include isolating infected individuals.
In the event of a weaponized viral hemorrhagic fever attack or outbreak, the Washoe
County Health District will work closely with the Nevada Division of Public and Behavioral
Health and the Centers for Disease Control and Prevention (CDC) to provide community partners and the public with recommendations regarding infection control activities. This information will be available through the media and the Washoe County Health District website.
Source: www.cdc.gov