1. Ebola Virus Outbreak
This presentation has been prepared by Christine H. Herrmann, Ph.D. of the Department of Molecular Virology and Microbiology at Baylor College of Medicine. It is intended for educational purposes and is suitable for use in middle and high school classrooms, as well as for general basic information regarding the Ebola virus outbreak.
This presentation will be updated periodically, but as this situation is changing rapidly, refer to the following websites for up-to-date information.
Centers for Disease Control and Prevention (CDC):
World Health Organization (WHO):
Department of Molecular Virology and Microbiology at Baylor College of Medicine:
Sources of information:
World Health Organization
Centers for Disease Control and Prevention
Dr. Peter J. Hotez, Professor of Molecular Virology and Microbiology and Pediatrics and Founding Dean of the National School of Tropical Medicine at Baylor College of Medicine.
2014

2. What is a Virus? Viruses are microscopic particles (10 – 400 nm).
Viruses are made of genetic material (DNA or RNA) surrounded by a protein coating and sometimes an outer layer containing lipids.
Viruses are not made of cells.
Viruses must infect cells to make more copies of themselves.
A virus cannot reproduce without infecting a cell and using the components of a host cell to make more copies of itself.
The new virus particles then infect other cells to continue to make more virus particles.
Antibiotics are not effective against viruses.
Photo: Generalized schematic of a virus particle
Additional Information:
A nanometer is one billionth of a meter.
Antivirals exist to treat some viruses, such as Tamiflu which is effective against most flu strains, and drugs that are used to treat HIV patients.

3. What is Ebola Virus?
Ebola virus is a member of a family of viruses called Filoviridae.
Ebola virus particles form long filaments.
The virus particles contain single-stranded RNA surrounded a lipid (fatty) membrane.
The new virus particles bud from the surface of the host cell.
Ebola virus was first discovered in 1976 near the Ebola River in Zaire (now the Democratic Republic of Congo).
There are four species of Ebola virus that cause disease in humans. The one causing the outbreak is a strain of the Zaire species.
Credit: NIAID
Photo: Ebola virus particles budding from an infected cell. Credit: NIAID
Additional Information:
Ebola belongs to the genus Ebolavirus of the family Filoviridae. The scientific name of the virus causing the current outbreak is Zaire ebolavirus.
Another member of the Filoviridae family is Marburg virus, which also causes a hemorrhagic fever.
Ebola virus filaments have a diameter of 80 nm and can be up to 14,000 nm in length.
Ebola virus contains single-stranded negative-sense RNA.
A fifth species of Ebola, the Reston strain, causes illness only in non-human primates. This species is the topic of the popular book, The Hot Zone by Richard Preston.

4. What is Ebola Virus Disease?
The disease caused by Ebola virus is called Ebola Virus Disease (EVD).
Ebola Virus Disease is considered a hemorrhagic fever disease, a type of disease caused by Ebola and other viruses that is characterized by bleeding and fever.
The symptoms of EVD include
Fever
Headache
Vomiting
Diarrhea
stomach pain
muscle pain
bleeding
Photo credit: Wikimedia Commons/Mikael Häggström  
Additional Information:
Other viruses that can cause hemorrhagic fever include Marburg, Lassa, and Dengue.
Credit: Wikimedia Commons

5. How do you get Ebola? It is not easy to catch Ebola virus.
An infected person is contagious only while they have symptoms.
To become infected, a person must have direct contact with blood or another body fluid, such as feces or vomit, from an infected person, or with an object that is contaminated with infected body fluids.
Following contact, the virus must enter an opening in the body, like a break in the skin or the eyes, nose, or mouth.
Ebola virus does not spread through the air, unlike flu.
In Africa, some people have become infected by handling bushmeat or through contact with infected bats.
Family members or healthcare workers are at highest risk of becoming infected.
Additional Information:
Contaminated objects include needles, syringes, medical equipment, clothing, or bedding.
Ebola virus also does not spread through water or by mosquitoes or other insects.
Bushmeat – wild animals hunted for food

6. How does Ebola make you sick?
Ebola virus infects certain cells of the immune system, so that they do not function properly. Instead of protecting a person from infection, they produce chemicals that cause harm.
Ebola virus also infects endothelial cells which line blood vessels.
Blood leaks out of damaged blood vessels.
Patients develop very low blood pressures and go into shock.
Patients usually die from shock due to fluid loss rather than actual blood loss.
Between 25 and 90 percent of patients with EVD die of the disease. In the current outbreak, slightly less than half of Ebola victims survive.
Credit: CDC
Photo: A cell type (macrophage) infected by Ebola virus. Credit: CDC
Additional Information:
Ebola infects monocytes and macrophages, cells of the immune system, which are then stimulated to produce high levels of cytokines (associated with fever and inflammation) which cause damage to blood vessels.
Ebola infection can also damage the liver and kidneys.

7. What is the treatment for EVD?
There is no cure for EVD.
There is no licensed vaccine for EVD.
There are experimental drugs and vaccines, but they have not been tested in humans, so it is not known how effective or safe they are.
The supply of experimental drugs is very limited, so there is an ethical dilemma regarding who should receive the drugs.
A few patients are receiving blood plasma from patients who have recovered from Ebola infection that contains antibodies to Ebola.
Patients in hospitals are given supportive care to maintain body fluids, salt levels , and blood pressure. This improves survival rates.
Credit: NIAID
Photo: Study Participant Receives Candidate Ebola Vaccine. Credit: NIAID
Additional Information:
Two experimental vaccines are being evaluated.
The testing of experimental drugs and vaccines is bypassing the normal regulatory processes due to the urgency of the situation.
Some experimental treatments have shown promising results in trials using monkey, but this does not guarantee their effectiveness in humans.

8. Where does Ebola come from?
Many viruses that infect humans emerged from animals.
A virus can be present in a host animal and not make them ill, but the virus can be passed to another animal or a person and make them sick.
The natural host of Ebola virus is thought to be the fruit bat, which in found in regions of Africa where outbreaks have occurred.
The first person in an outbreak becomes infected through contact with an infected animal.
The virus can then spread from person to person.
Credit: WHO
Photo: Bat captured in Uganda. Credit: WHO
Additional Information:
Diseases that arise when infectious agents in animals are passed to humans are referred to as zoonoses.
As population numbers increase and humans spread into new geographical regions and habitats, the possibility of humans coming into close contact with animal species that are potential hosts of an infectious agent increases.
The animal host that harbors the infectious agent is known as the reservoir.

9. Why is EVD called an emerging disease?
EVD is considered an emerging infectious disease.
An emerging infectious disease is one that has recently been detected, or a known one that has appeared in a new place, or one that is spreading rapidly.
Emerging infections can be caused by previously unknown viruses (or other infectious agents such as bacteria) or viruses that spread to new locations.
Other examples of emerging viruses are SARS, MERS, flu, HIV, and Chikungunya virus.
Credit: NIAID
Photos: top – MERS; bottom – influenza (flu) virus particle
For more information on emerging infectious diseases, see
Credit: CDC

10. When and where was Ebola discovered?
Ebola was first recognized in 1976 when it caused two separate outbreaks – one in Zaire (now the Democratic Republic of Congo) and the other in southern Sudan.
The outbreaks were caused by different species. The Zaire virus caused deaths in 90% of infected people; the Sudan virus caused deaths in 50%.
Since then, there have been about 20 outbreaks of Ebola in central Africa with a total of around 2400 cases and 1600 deaths.
Because the prior outbreaks occurred in remote areas, they were easier to contain.
Credit: CDC
Photo: Residents in a village in Zaire during 1976 Ebola outbreak. Credit: CDC/Lyle Conrad
Map: Wikimedia Commons/Zorecchi
Additional Information:
In addition to the Democratic Republic of Congo and Sudan, prior outbreaks have also occurred in Uganda, Congo, Gabon, and Ivory Coast. Outbreaks in these countries were caused by four different species of Ebola virus.
Credit: Wikimedia Commons

11. How did the current outbreak begin?
The first person to become infected was a two year old boy living in Guinea in December 2013.
The Ebola outbreak was officially recognized in March 2014 in Guinea and then quickly spread to Liberia and Sierra Leone.
A man traveling by plane brought Ebola from Liberia to Nigeria and there were several cases there and one in Senegal.
Ebola continues to spread rapidly in Liberia, Sierra Leone, and Guinea.
As of October 12, there have been around 9000 cases and 4500 deaths.
Photo: Wikimedia Commons/Mikael Häggström
Additional Information:
The outbreak appears to have been successfully contained in Senegal and Nigeria.
Rates of transmission are increasing at an alarming rate in Liberia, Guinea, and Sierra Leone. It has been projected that there could be 10,000 new cases per week by the end of the year.
The most cases and deaths have occurred in Liberia.

12. Map showing case numbers in West Africa
Source: Wikimedia Commons/Mikael Häggström
For updated map, see
For other maps, see
Credit: Wikimedia Commons
The most cases and deaths have occurred in Liberia, followed by Sierra Leone, and then Guinea. The rate of new infections is still increasing in these three countries.

13. Why is this outbreak so bad?
It started near the borders of three countries where there is a lot of travel.
It started in countries where Ebola had not been seen before, so it was not recognized at first.
It went into very densely populated cities where the virus could spread easily.
It began in countries with weak healthcare systems that did not have enough hospital beds or isolation equipment, and many healthcare workers became ill and died.
Response from governments and other agencies was too slow.
It spread to new countries by air travel.
Credit: CDC
Photo: Beds in an Ebola isolation center in Sierra Leone. Credit: CDC/Sally Ezra
Additional Information:
Early symptoms of Ebola can be mistaken for malaria or other diseases found in that region.

14. How did Ebola spread to the U.S.?
Ebola spread to the United States when a man from Liberia who had contact with an Ebola victim flew to Dallas, Texas.
He developed symptoms after arriving in the U.S.
The hospital did not recognize his illness as Ebola and sent him home.
He returned three days later, was admitted to the hospital, and died ten days later.
A nurse who treated this patient tested positive for the virus. This was the first transmission within the U.S. A second nurse has also been diagnosed with Ebola.
A number of Ebola patients are being treated in several locations in Europe. There has one case of infection of a healthcare worker that occurred in Spain.
Additional Information:
Infection of the nurse in Spain was the first instance of Ebola transmission outside of Africa. She has recovered from Ebola infection, and tests are negative for the presence of the virus in her body.
The nurses infected in Dallas were transported to specialized isolation units for treatment. There are four such specialized isolation units in the United States; they are in Maryland, Georgia, Nebraska, and Montana.

15. How will the outbreak be stopped?
Tracing of all people who had close contact with an infected person while they were showing symptoms
Isolation of all infected people with symptoms
Improved personal safety procedures and training for healthcare workers and complete compliance with these safety procedures
Production of drugs and vaccines
Containment of the Ebola outbreak in West Africa to prevent further spread to other countries
Learning from this outbreak how to limit future outbreaks of Ebola or other emerging viruses
Credit: CDC
Photo: Healthcare worker being assisted with personal protection equipment prior to entering an Ebola treatment center in Liberia. Credit: CDC/Sally Ezra