- Safety and Health Topics
The most common routes of transmission of Ebola viruses are:
- Contact of the eyes or other mucous membranes with blood or body fluids of a person or animal with Ebola virus disease (EVD);
- Contact with contaminated equipment or other objects; and
- Ingestion of infectious blood or body fluids.
Ebola virus is believed to be viable outside of the body for several days. An evaluation of the persistence of certain Category A select agents in the environment suggests that viruses of the family Filoviridae, of which Ebola viruses are members, may remain stable for 4-5 days in dried blood.2
Though transmission through inhalation of airborne virus is not currently a primary concern during naturally-occurring outbreaks, it may be possible for Ebola virus to be aerosolized under certain conditions. CDC has provided guidance for healthcare workers who must perform aerosol-generating procedures on patients known to have or suspected of having EVD. Pathogenicity (i.e., how the virus acts on the body to cause disease) and symptoms are typically the same regardless of the initial route of infection with Ebola virus.
In all settings, avoid using compressed air or water when cleaning surfaces, as it might cause droplets containing infectious material to become airborne (i.e., create a bioaerosol).1
Symptoms of Ebola typically appear within 2-21 days (8-10 days is most common) following infection, and the illness runs its course within 14-21 days of symptom onset. The table below describes the natural history of Ebola:
|Exposure||Incubation||Symptom Onset||Illness||Recovery or Death|
- Exposure to Ebola virus through contact with infectious blood or body fluids, contaminated environmental surfaces, or an infected individual or animal.
- In some instances, exposure may be due to aerosolized viral particles.
- Exposed individuals are not contagious.
- Virus multiplies within the body before symptoms develop.
- Individuals become contagious when symptoms appear.
- Initial symptoms of EVD may include fever, fatigue, muscle pain, headache, and sore throat.
- Symptoms appear similar to other viral illnesses.
- Illness progresses to include nausea, vomiting, diarrhea, impaired organ function, and blood count changes.
- Some cases experience a rash and internal and/or external bleeding (e.g., from skin, eyes, or gums).
- The bodies of individuals who die from EVD remain infectious after death, and must be handled accordingly during death care.
- Individuals who recover from EVD generally are no longer contagious. However, Ebola virus may be found in certain body fluids, such as semen and ocular fluid (fluid inside the eye), even after an individual has recovered.
Up to 49 days
As the infection progresses, patients often experience a rash and severe bleeding as the blood loses its ability to coagulate and blood vessel membranes become more permeable. Lymphocyte counts drop and neutrophils spike. Ebola patients ultimately die from diffuse bleeding and shock.
Medical Management and Countermeasures
Individuals who may have come into contact with Ebola virus may be quarantined at the discretion of public health officials. Isolate suspected and confirmed cases of EVD to prevent transmission of the disease to other individuals. If possible, isolating suspected cases separately from confirmed cases also may help prevent transmission.
Healthcare providers have a variety of tools at their disposal to test for Ebola virus infection and diagnose EVD, including blood tests that can detect antibodies to the Ebola virus or the RNA of the virus itself. Cell culture and electron microscopy are also used to identify Ebola virus.
For individuals who become infected with EVD, there is currently no treatment, antiviral therapy, or approved vaccine. Supportive hospital care for patients with EVD (like other viral hemorrhagic fevers) includes fluid and blood replacement, maintaining stable blood pressure, and treating other comorbidities (i.e., other injuries or infections) as appropriate.
Some experimental vaccine and pharmaceutical products have been used to combat recent EVD outbreaks, including an experimental vaccine deployed in Central Africa to contain the current outbreak and an experimental drug (specifically, a preparation of antibodies) used to treat infected patients.
The U.S. Department of Health and Human Services is prioritizing the development of vaccines and other medical countermeasures for EVD and Ebola virus accordingly.3 The National Institutes of Health (NIH) has had some success with experimental vaccines in non-human primate models. Ongoing Research into recombinant adenoviruses, recombinant vesicular stomatitis viruses (VSVs), and other recombinant vaccine products is underway, but further work is needed to demonstrate safety and efficacy and, if appropriate, secure approval for their use.4 Research efforts continue in a number of nations to develop an effective vaccine and other medical countermeasures, such as antibody serum, to prevent or treat EVD and related diseases.
CDC's Ebola page provides the most up-to-date information on medical aspects of Ebola virus infection and EVD.
1 Preventing Spread of Disease on Commercial Aircraft: Guidance for Cabin Crew. Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services (HHS).
2 Sinclair, R., Boone, S. A., Greenberg, D., Keim, P., & Gerba, C. P. (2008). Persistence of category A select agents in the environment. Applied and environmental microbiology, 74(3), 555-563.
3 "Public Health Emergency Medical Countermeasures Enterprise (PHEMCE) Strategy," U.S. Department of Health and Human Services, accessed April 12, 2014.
4 Thomas Hoenen, Allison Groseth, and Heinz Feldmann, "Current Ebola vaccines," Expert Opinion on Biological Therapy 12, no. 7 (2012): 859-872.