Of the people who contract Ebola, 25 to 90 percent eventually die from the disease, according to the World Health Organization (WHO).
The Ebola virus is one of two identified members of the Filoviridae family of viruses. The other is Marburg virus — both viruses can cause hemorrhagic fever, a serious condition in which the blood vessels leak, leading to hemorrhage, or heavy bleeding, and eventual shock and death due to the inability of organs to function properly.
Five strains of the Ebola virus have been identified: Tai Forest (formerly called Ivory Coast), Sudan, Zaire, Reston, and Bundibugyo. Only Ebola-Reston does not cause severe disease in humans.
Ebola is carried by animal hosts (such as bats and monkeys) in Africa and can occasionally make the jump to humans. Exactly how that happens is not yet known.
Symptoms of Ebola may start anywhere from two to 21 days after infection with the virus. In most cases, symptoms start within five to 10 days. Early signs and symptoms of Ebola may be mild and nonspecific:
- Low fever
- Mild queasiness or feeling of being ill
More severe signs and symptoms emerge as the virus begins to replicate in the host and cause the blood vessels to leak:
- High fever
- Muscle aches
- Bleeding from the gums, nose, rectum, and internal organs
- Low blood pressure
Ebola Virus Transmission
Humans are not infectious, meaning they cannot transmit the disease to another person, until they have symptoms.
Once a person is symptomatic, the Ebola virus is transmitted from person to person through contact with an infected person's bodily fluids and secretions, such as blood, vomit, and feces, and any materials (clothes, bedding, etc.) contaminated with those fluids.
Airborne transmission, like coughing or sneezing, has not been shown to spread Ebola among humans. Family members of people with Ebola and healthcare professionals who treat them are at particularly high risk of contracting the disease because of their close contact with the sick person.
Laboratory workers are also at risk when handling blood and other samples taken from infected people.
Measures that can be taken to prevent the spread of Ebola include:
- Isolating infected patients from anyone who doesn't have Ebola
- Having healthcare workers wear protective gear, including gloves, masks, goggles, gowns, and other clothing, while caring for Ebola patients
- Decontaminating or destroying any surfaces or materials a patient has contacted, including syringes, needles, and other medical equipment
- Cleaning healthcare workers with a disinfectant such as chlorine, which kills the Ebola virus
- Encouraging Ebola survivors, who are believed to be immune to the strain of Ebola they had, to help care for people who are sick with Ebola and/or bury those who die
- Monitoring anyone who has come into contact with an Ebola patient
Ideally, people who have had contact with an Ebola patient — in or out of a hospital — are monitored for signs of the infection for at least 21 days after their last contact.
In some cases, close contacts have been quarantined until the 21-day incubation period has passed to make sure they don't spread the virus on to others.
People remain infectious as long as the virus is present in their blood and body fluids, including semen and breast milk. According the WHO, men who have recovered from Ebola can spread the virus through their semen for several months following recovery.
In 2015, a doctor who had been treated for an Ebola infection was found to carry the virus in his eye, months after he was declared clear of the virus in 2014. Experts are researching this and other long-lasting effects of Ebola infection and "post-Ebola syndrome."
Ebola Treatment and Cure
There is no known cure for Ebola, but some people do survive it and are then thought to be immune to the strain they had. How long this immunity lasts is not known.There is also no vaccine for Ebola virus, although two potential vaccines are currently being tested, according to the WHO.
The main treatment for Ebola is supportive care, including the administration of intravenous fluids, transfusions of red blood cells and other blood products if necessary, and treatment of symptoms, when possible. Some patients require dialysis and mechanical ventilation if they are critically ill.
Two experimental treatments have been tried in the 2014 Ebola outbreak:
Blood plasma: The plasma from an Ebola survivor has been transfused into several patients, with hopes that the antibodies from the survivor will help fight the virus in those currently infected.
While the patients who have received plasma transfusions have thus far survived, it is not known what role the plasma transfusions played. The idea of using blood plasma from Ebola survivors as treatment is not new, and the approach has been used in small numbers of patients in previous Ebola outbreaks, with apparently good results.
ZMapp: Two Americans who survived were treated with the experimental drug ZMapp, developed by Mapp Biopharmaceutical, Inc. The drug is a combination of three monoclonal antibodies that bind to the protein of the Ebola virus. ZMapp has not yet been tested in humans for safety or effectiveness, and very little of the drug was available during the 2014 Ebola outbreak.