2014 Ebola Virus Outbreak

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.

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

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 Credit: Wikimedia Commons

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. How do you get Ebola?

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

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. What is the treatment for EVD? Credit: NIAID

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

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 Credit: CDC

When and where was Ebola discovered? Credit: CDC 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: Wikimedia Commons

How did the current outbreak begin? The first person to become infected was a two year old boy living in Guinea in December The Ebola outbreak was officially recognized in March 2014 in Guinea and then quickly spread to Liberia and Sierra Leone. There have been a small number of cases in Nigeria, Senegal, and Mali, but almost all cases have been in Liberia, Guinea, and Sierra Leone. Ebola transmission has stabilized in Liberia and Guinea, but remains intense in Sierra Leone. By the beginning of December, there have been in total more than 17,000 cases and 6,000 deaths.

Credit: Wikimedia Commons Map showing case numbers in West Africa The most cases and deaths have occurred in Liberia, followed by Sierra Leone, and then Guinea. The rate of new infections is slowing in Liberia and Guinea but still increasing in Sierra Leone.

How did Ebola spread to the U.S.? Ebola spread to the United States when a Liberian man 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 was also diagnosed with Ebola. Both nurses recovered. No further transmission occurred. A few patients who became infected in West Africa have been treated in several locations in the United States and Europe. In one case, a healthcare worker became infected in Spain, but no other new infections occurred.

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 had a chance to spread before it was recognized. 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

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 Implementation of safe burial 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