What are viral hemorrhagic fevers?

Viral hemorrhagic fevers are a group of diseases caused by four distinct families of viruses: arenaviruses, bunyaviruses, filoviruses and flaviviruses. The usual hosts for most of these viruses are rodents or arthropods (such as ticks and mosquitoes) but, in some cases, such as Ebola virus, the natural host is unknown. All forms of the disease begin with fever and muscle aches. Depending on the particular virus, the disease can progress until the patient becomes very ill with respiratory problems, severe bleeding, kidney problems and shock. The severity of viral hemorrhagic fever can range from a relatively mild illness to death.

What is Ebola virus?

Ebola virus is a member of the filovirus family. When magnified several thousand times by an electron microscope, these viruses appear as long filaments or threads. Discovered in 1976, Ebola virus was named for a river in Zaire, Africa, where it was first detected.

How common is Ebola virus hemorrhagic fever?

Until recently, only three outbreaks of Ebola hemorrhagic fever among people had been reported. The first two outbreaks were in 1976: one in Zaire and one in western Sudan. These were large outbreaks, resulting in more than 550 cases and 340 deaths. The third outbreak, in 1979 in Sudan, was smaller, with 34 cases and 22 fatalities. During each of these outbreaks, a majority of cases occurred in hospital settings under the challenging conditions of the developing world. These conditions, including a lack of adequate medical supplies and the frequent reusing of needles and syringes, played a major role in the spread of the disease. The outbreaks were quickly controlled when appropriate medical supplies and equipment were made available and quarantine procedures were used. The source of the Ebola virus in nature remains unknown. In an attempt to identify the source, investigators tested thousands of specimens from animals captured near the outbreak areas, but their efforts were unsuccessful. Monkeys, like humans, appear to be susceptible to infection and, if infected, may serve as a source of the virus.

What do we know about the recent outbreak of Ebola virus infection?

The recent Ebola virus outbreak is centered in Kikwit, Zaire, a city of 400,000 located about 250 miles east of the capital city of Kinshasa. The outbreak appears to have started with a patient who had surgery in Kikwit on April 10, 1995. Members of the surgical team then developed symptoms similar to those of a viral hemorrhagic fever disease. A Belgian physician suspected Ebola hemorrhagic fever and reported the disease to the Zairian government. At the request of Zairian health officials, medical teams from the U.S. Centers for Disease Control and Prevention, the World Health Organization, and from Belgium, France and South Africa are collaborating to investigate and control the outbreak in Zaire.

What are the symptoms of Ebola hemorrhagic fever?

Initial symptoms, which begin four to 16 days after infection, include fever, chills, headaches, muscle aches and loss of appetite. As the disease progresses, vomiting, diarrhea, abdominal and chest pain, and sore throat can occur. The blood fails to clot and patients may bleed from injection sites as well as into the gastrointestinal tract, skin and internal organs.

How is the Ebola virus spread from person to person?

Ebola virus is spread through close personal contact with a person who is very ill with the disease. In previous outbreaks, person-to-person transmission frequently occurred among hospital care workers or family members who were caring for an ill person. The virus also has been spread through the reuse of hypodermic needles in the treatment of patients. Reusing needles is a common practice in developing countries, such as Zaire and Sudan, where the health care system is underfinanced. U.S. medical facilities do not reuse needles.

Close personal contact with persons who are infected but show no signs of active disease is very unlikely to result in infection. Patients who have recovered from an illness caused by Ebola virus do not pose a serious risk for spreading the infection. However, the virus may be present in the genital secretions of such persons for a brief period after their recovery; therefore, it is possible for the virus to be spread through sexual contact.

How is Ebola hemorrhagic fever diagnosed?

Diagnosis is made by detecting Ebola antigens, antibodies or genetic material or by culturing the virus from clinical specimens. These specimens usually have been treated to inactivate (kill) the virus. Research on Ebola virus must be done in a special high-containment laboratory to protect scientists working with infected tissue.

How will health officials control the outbreak?

Previous outbreaks of Ebola hemorrhagic fever have been successfully controlled by isolating sick persons. Those who care for these patients must wear masks, gowns and gloves; needles and syringes must be carefully sterilized; and wastes and corpses must be disposed of properly.

How do hospital personnel isolate an ill person?

Hospital personnel isolate ill persons through a method called "barrier technique," which entails the following actions: 1) doctors and nurses wear gowns, masks, gloves and goggles when caring for patients; 2) the patient's visitors are restricted; 3) disposable materials are removed from the room and burned after use; 4) all reusable materials are sterilized before reuse; and 5) since the virus is easily destroyed by disinfectants, all hard surfaces are cleaned with a sanitizing solution.

Are persons in the United States at risk?

Persons in the United States are at risk only if they have had close personal contact with patients in Zaire who are infected with Ebola virus. There are no reports that infected persons have left the country of Zaire. The Zairian government has quarantined all persons in the affected areas and restricted movement of persons in and out of these areas. Any persons who wish to travel to Zaire are encouraged to contact the U.S. State Department (202-647-5225) for travel advisories.

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