An Ebola Explainer

Ebola has been much in the news recently and it has been the subject of a lot of fear regarding possible outbreaks in the United States. Ebola was originally called Zaire Ebolavirus, named after the Ebola river in what is now the Democratic Republic of Congo. The area surrounding the Ebola river was the site of the first recorded outbreak.

Electron micrograph of Ebola virion
Electron micrograph of Ebola virion
(source Wikimedia commons)

In order to understand Ebola, I think it’s important to understand how viruses work. A virus is a small particle that can infect and replicate only in living cells. A virus particle (virion) is made up of RNA or DNA surrounded by a protein coat called the capsid and sometimes a lipid layer called an envelope that can facilitate infection. Upon introduction, molecules on the surface of a molecule recognize molecules on specific cell types; the membrane of the virus essentially fuses to the target cell. The capsid is removed and viral proteins co-opt the cellular machinery to replicate its genome to replicate the virus. Interestingly, there is a debate as to whether viruses are alive or not. Although viruses have a genome and undergo evolution through natural selection, they do not have a cellular structure and are not capable of reproducing on their own.

Electron micrograph images of virus structures
Electron micrograph showing the capsid of adenoviruses.
(Source Wikimedia Commons)

Viruses are dealt with in multiple ways. RNA interference is one way. Most viruses utilize a double stranded RNA genome and the host’s (the infected individual) own genome produces short, non-protein producing single stranded RNA sequences (called microRNA or miR). These miRs target the virus’ RNA genome and sequester and degrade the genes that code for proteins involved in viral replication. Another method is the production of antibodies. The host’s adaptive immune system develops antibodies, which are molecules capable of binding to the virus and preventing it from being infectious. Finally, T cells can recognize virus molecules or proteins (called an antigen), become a Killer T cell and destroy the virus, while ramping up production of the specific types of T cells that can recognize and kill the virus.

Scanning electron micrograph of a T Cell
Scanning electron micrograph of a T Cell
(Source Wikimedia Commons)

Ebola has a single stranded RNA genome about 19000 nucleotides long. For comparison, the human genome has more than 3 billion base pairs. Ebola enters into the cell the same way most viruses do, although there are multiple proteins believed to be important in the ability of the virus to attach and fuse to host cells. It is important to research and identify those proteins because if scientists can target those proteins, they may be able to disrupt the ability of the virus to attach to and stop viral replication and essentially stop the infection. After viral replication occurs, the new virions bud out of the cells to infect more cells.

Flowchart of the viral replication process
Virus attaching to the cell, replicating and budding.

Here it would be useful to have a short discussion about what infectious versus contagious mean in terms of viral infections. Infections are caused by viruses that disrupt the normal ways our cells work. Some infections, such as Ebola or chickenpox, are diseases that can be passed from person to person by direct physical contact or with contact with an item an infected person has touched. These are contagious diseases. Infectious diseases are a little more scary in that individuals can contract the disease even if they do not come in direct contact with an infected person. Rather, infectious diseases can be spread through a sneeze, as in the case of a cold or flu. Ebola is only spread through direct physical contact with the bodily fluids of an infected person, meaning the virus is contagious but not infectious.

While Ebola is contagious, it is not terribly much so. In fact, scientists believe that direct physical contact between an infected and non-infected individual is the only way to spread the virus. While it is possible that touching a drop of saliva or blood from an infected individual could transmit Ebola, it is not likely. Any individual who has been infected with Ebola remains able to spread the virus as long as the virus is present. The World Health Organization states that men can retain virus in their semen for up to 7 weeks.

With regard to treatment of Ebola, there is currently no vaccine available. However, there are studies working to test the drug ZMAPP, the main Ebola drug made up of a cocktail of antibodies. Experiments in animals have indicated there may be therapeutic promise. While the patients treated at Emory Hospital were given the drug, it is not known whether the drug was actually efficacious treating the disease. Long term studies must be performed to know for certain.

Three people in full-body protective gear, including respirator masks and goggles
Personal protective equipment for treatment of Ebola patients

The symptoms of Ebola are a fever (greater than 101.5F), headaches, muscle pain, diarrhea, vomiting, abdominal pain and unexplained bleeding or bruising. Typical medical interventions are intravenous application of fluids and electrolytes, maintaining oxygen and breathing and treating other infections that may occur. Unfortunately, for the most part, recovery from Ebola relies on good, supportive treatment and the individual’s immune system. Individuals who recover from infection have antibodies that protect them for at least 10 years.

The reasons behind the outbreak and the difficulty containing it are myriad and diverse. Mainly, cultural practices, a lack of understanding about transmission of the disease, coupled with the remoteness of some of the sites of outbreak, lack of funding for protection equipment for health care workers and lack of funding for treatments, as well as dearth in health care workers available to care for infected individuals have created a perfect storm.

I hope you understand a bit more about Ebola, I am happy to answer questions to the best of my ability. If you want to help, there are places to donate money such as the Red Cross and Doctors Without Borders. Charity watch additionally has a list of good places to send your money.

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