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Biological Warfare (cont.)

Viral Hemorrhagic Fevers

Viral hemorrhagic fevers are caused by four families of viruses.

  • Arenaviridae (Lassa, Argentine, Bolivian, Brazilian, Venezuelan hemorrhagic fevers)
  • Bunyaviridae (Rift Valley, Crimean-Congo, Hantaan)
  • Filoviridae (Marburg, Ebola)
  • Flaviviridae (Yellow, Dengue, Kyasanur Forest, Omsk HFs)

The best known of the viral hemorrhagic fevers is Ebola virus. First recognized in Zaire in 1976, the virus has been linked to at least 20 outbreaks in Africa. A majority of people who contract Ebola will die. A related virus was discovered in Reston, Va., in 1989 in association with an outbreak of illness among monkeys imported from the Philippines. No human cases occurred with this outbreak. In 2012, an outbreak of Ebola started in Uganda and now has spread to Democratic Republic of the Congo. The largest outbreak of Ebola virus in history began in 2014, located primarily in the western African countries of Sierra Leone, Guinea, and Liberia. It has resulted in thousands of deaths, and unless contained, is projected to reach more than 1 million victims by early 2015.

These viruses are each characterized by an acute generalized illness that includes feeling quite ill (flulike illness) with profound exhaustion and often associated internal bleeding. Most agents are highly infectious via the aerosol route, and most are stable as respiratory aerosols. Thus, they possess characteristics that may make them attractive for use by terrorists. However, Ebola virus has not been demonstrated to be contagious person-to-person through an aerosol route. It is spread through direct contact with the blood or other body fluids of an infected person, including a corpse.

The agents that produce viral hemorrhagic fever are all simple RNA viruses. They are able to survive in blood for long periods, which means they can infect people who are around animals slaughtered domestically. These viruses are linked to the rodents, bats, or insects that help to spread them, which helps in searching for a diagnosis.

The specific viral hemorrhagic fever manifestations that develop depend on many factors such as the strength of the virus, its strain, and the route of exposure.

Signs and Symptoms

All viral hemorrhagic fevers primarily target blood vessels. They damage the blood vessels and produce internal bleeding. Victims may have fever, aches, exhaustion, infected eyes, low blood pressure to severe shock, and bleeding in tiny blood vessels such as in the eye. More severe cases will have serious problems with the nervous system, liver, and lungs.

Depending on the type of virus, symptoms can include deafness, severe internal bleeding, kidney failure, rash, black (bloody) vomit, and other life-threatening symptoms.

Diagnosis

It is important for the doctor to know a person's travel history in making a diagnosis of viral hemorrhagic fever. These agents are linked tightly with their natural geographic area and the ecology of the species and vectors found in that specific locale. Victims often recall exposures to rodents (Arenavirus, Hantavirus), mosquitoes (Valley fever virus, yellow and dengue fever viruses), or even slaughtered horses (Rift Valley fever virus, Crimean-Congo virus).

Laboratory tests may be helpful. Testing can be conducted at the CDC in Atlanta or the U.S. Army Medical Research Institute of Infectious Disease (USAMRIID) at Fort Detrick in Frederick, Md.

Treatment

Treatment for viral hemorrhagic fevers is largely directed at easing the discomfort of the symptoms. Victims benefit from being placed in a hospital setting immediately. Air transport is not advised. Sedative and pain-relieving medications are helpful, but aspirin and similar drugs should not be given because of their tendency to make bleeding worse.

Doctors will also not usually use IV lines or catheters because of bleeding problems. The treatment for bleeding is controversial. Generally, mild bleeding is not usually treated, but severe bleeding requires appropriate replacement therapy (blood transfusions through an IV line).

Specific treatment with ribavirin has been used and is currently under investigation as a therapy for Lassa fever, hantavirus, Crimean-Congo, and Rift Valley fever. Treatment is most effective if begun within seven days. Ribavirin has poor activity against the filoviruses and flaviviruses.

Prevention

The only established and licensed virus-specific vaccine against any of these viruses is the yellow fever vaccine. It is mandatory for those traveling into areas of Africa and South America where the disease is commonly found. Current trials are underway for further vaccines and antibody therapies.

Medically Reviewed by a Doctor on 12/3/2014

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