The Ebola virus was first associated with an outbreak of 318 cases of a hemorrhagic disease in Zaire. Of the 318 cases, 280 of them died—and died quickly. That same year, 1976, 284 people in Sudan also became infected with the virus and 156 died.
The viruses that cause Ebola and Marburg are similar, infecting both monkeys and people. The outbreaks of these diseases are often self-contained, however, because they kill their hosts so quickly that they rapidly run out of people to infect.
The Zaire strain of Ebola virus has a mortality rate of 88 percent, which is higher than either the Sudan strain of Ebola or the Marburg virus.
A closely related virus, called Reston, was isolated from animals in the Philippines, indicating that these diseases are not completely confined to Africa. So far, Reston has not been found to cause disease in people.
The Ebola virus spreads through the blood, multiplying in many organs. It causes severe damage to the liver, lymphatic system, kidneys, ovaries, and testes. Platelets and linings of arteries are severely damaged, which results in profuse bleeding. Mucosal surfaces of the stomach, heart membrane, and vagina are also affected. Internal bleeding results in shock and acute respiratory distress, leading to death.
Once a patient is infected with Ebola, the incubation period is 4 to 16 days. The onset of disease is sudden, with fever, chills, headache, anorexia, and muscle pain. As the disease progresses, nausea, vomiting, sore throat, stomach pain, and diarrhea are common. Most patients develop severe hemorrhages, usually between days five and seven. Bleeding occurs from multiple sites, including the digestive tract, lungs, and gums. Death occurs within 7 to 16 days.
The Ebola virus was named after the Ebola River, in the Congo. The disease has occurred in Congo, Sudan, the Ivory Coast, and Uganda. There has never been a case in the United States.
Some people recover from Ebola. No one fully understands why.
Epidemics result from person-to-person contact within communities, families, and hospitals, or from inadvertent laboratory exposures. The means of infection and the natural ecology of these viruses are largely unknown, although an association with monkeys and/or bats has been suggested.
Marburg, Ebola, and Reston viruses can be isolated from the blood of people who are infected. They produce distinct antibody responses that are easy to detect. These antibodies appear 10 to 14 days after initial infection. Unlike most other infectious agents, there is significant risk to health-care workers and laboratory technicians in handling and processing blood or tissue samples infected with Ebola.
The index case is the first case of disease in an outbreak. If epidemiologists can find the index case, sometimes it helps them figure out how a disease began to spread.
There are no drugs that work against these diseases, and there is no known vaccine. Therapy involving blood plasma from people who have recovered, anticoagulation agents, which attempt to reduce hemorrhaging, and interferon have been used with limited success. Their effectiveness remains controversial.
The most effective way to reduce or prevent transmission in an outbreak is through the proper use of barrier protection for doctors and nurses. This includes the use of gloves and masks, with gloves being changed after every patient. Another important protection in a hospital is being sure all equipment is properly sterilized.
People don't carry the virus. They get sick and their infected blood and bodily fluids infect others.