Hemorrhagic Fevers
Hemorrhagic fevers are serious viral infections characterized by bleeding. These infections occur primarily in parts of Africa and South America.
Several groups of viruses, including filoviruses and arenaviruses, can cause fever and other symptoms that are accompanied by bleeding (hemorrhagic fever). Bleeding occurs because the viruses make the blood vessels leak. These infections are often fatal.
Ebola Virus and Marburg Virus: These two dangerous African viruses are classified as filoviruses. The original source of these viruses in nature (the host) is not known. However, the first infections of people with Marburg virus were thought to come from monkeys.
Both viruses can be spread from person to person by contact with skin, body fluids such as blood, or other infected body tissues. Family members and health care workers are most likely to be infected.
Symptoms begin 2 to 21 days (usually 5 to 10 days) after exposure. They include fever, muscle aches, headache, vomiting, diarrhea, cough, rash, and swollen glands. Bleeding under the skin can be seen as purplish spots or patches, and the gums, nose, rectum, or internal organs may bleed, as may puncture wounds.
Ebola or Marburg viral infections may cause delirium, coma, and low blood pressure and are often fatal. From 25 to 90% of infected people die. Ebola infection is more likely to be fatal.
Doctors suspect one of these infections in people who bleed easily, have typical symptoms (fever, low blood pressure, delirium, or coma), and have recently traveled to areas where the infections are common. Blood tests to identify the virus help confirm the diagnosis. Samples of blood or infected tissue, especially liver tissue, may be examined under a microscope.
No vaccine is available, but one is being studied. The only treatment for these infections is general supportive care, which includes giving intravenous fluids and other treatments to maintain body functions. Recovery takes a long time. Strict isolation is necessary to prevent further spread. These viruses have not yet spread to large regions, but such spread is always a concern.
Lassa Fever and South American Hemorrhagic Fevers: Caused by arenaviruses, these infections spread from rodents or their urine or droppings to people, usually when contaminated food is eaten. They can spread from person to person through contact with body fluids (such as saliva, urine, feces, or blood). Lassa fever occurs mainly in West Africa. The South American fevers are confined mostly to Bolivia and Argentina.
The infections cause fever, a general feeling of illness (malaise), chest pain, diffuse body aches, and vomiting. Bleeding from the mouth, nose, stomach, and intestinal tract is common in the South American hemorrhagic fevers. Overt bleeding is less common in Lassa fever. But bleeding sometimes occurs from puncture wounds, the gums, or the nose and often occurs under the skin (seen as small purplish spots). When death occurs, it usually results from shock caused by diffuse leakage of fluid from blood vessels.
These infections are often fatal. About 2% to 20% of people with Lassa fever die. In women who are pregnant or have just had a baby, the death rate is higher (up to 92%). These infections are suspected when people who may have been exposed to the virus have characteristic symptoms. The diagnosis is confirmed by blood tests to identify the virus or antibodies to the virus.
Strict isolation is required to prevent spread to health care workers and family members. An experimental vaccine is effective against some South American hemorrhagic fevers. Treatment is supportive care, which includes giving fluids and electrolytes if needed.
http://www.merck.com/mmhe/sec17/ch198/ch198i.html
