The Biology of Ebola

The Biology of Ebola

The 2014 West African Ebola epidemic is the largest recorded outbreak. With 8,400 documented cases and over 4,000 deaths worldwide, many are trying to pinpoint why the epidemic is worse than in past cases.

Ebola hemorrhagic fever is a deadly disease affecting humans and non-human primates. The Ebola virus belongs to the family Filoviridae and include three genera: Cuevavirus, Marburgvirus, and Ebolavirus. Five species that have been identified include: Zaire, Bundibugyo, Sudan, Reston, and Taï Forest.

Ebola was only fairly recently discovered— in 1976 the virus appeared in Sudan and the Democratic Republic of Congo. The outbreak in the DRC was located near the Ebola River, where the virus takes its name. Since 1976 there are have sporadic outbreaks throughout Africa, with the Zaire, Bundibugyo, and Sudan strains most prevalent. Incubation of the Ebola virus takes about 2 to 21 days. Symptoms include sudden fever fatigue, muscle pain, headache, and sore throat.

Further symptoms are more severe: vomiting, diarrhea, rash, and internal and external bleeding. Infected humans are not contagious until symptoms are present. Transmission from human to human comes through direct contact through bodily fluids (blood, secretions, etc) and with surfaces and materials contaminated with these bodily fluids. The current outbreak is believed to have started over hunting fruit bats.

The current outbreak of the Ebola virus in Liberia belongs to the Zaire species and is suspected to have originated in a small village near the Guinea border. For the people of Guinea, Sierra Leone, and Liberia, the concept of a border is fluid, not static. Many citizens of each country pass through the borders to visit family members and markets, and individuals who make frequent trips across these countries can infect many.

Efforts to control the spread of the Ebola virus are often hampered by beliefs held by the people of West Africa. In certain parts of West Africa there is a belief that by saying the word ‘Ebola’ aloud causes the disease to appear. Healthcare workers, even doctors, are oftentimes viewed with distrust. Sadly, during past outbreaks, healthcare workers who did not pay attention to regulations often became carriers of the virus, further spreading the virus’ impact in surrounding areas.

According to Doctors without Borders, in order to contain the spread of Ebola there must be trust with not only the patient but with the patient’s family as well. The lack of trust coupled with miscommunication and misinformation about the virus hinders relief efforts. Many doctors say religious and government officials must spread information regarding Ebola for people to know the signs and seek medical attention. Another issue is burial rites. Like Western culture, the people of West Africa bathe and dress the dead. Ebola is still present in a body after death, and close contact with it can lead to transmission. In the past months, raids have been prevalent, with looters taking mattresses and blankets covered in fluids from the patients and threatening the effectiveness of containment.

It’s not just West Africans who are at risk: doctors working with patients, while covered head to toe with protection such as hazmat suits and goggles, are also at risk infection. Temperatures inside protective gear puts doctors at risk for hyperthermia and dehydration. There’s also a shortage of experienced doctors to help treat Ebola hard-hit areas and in newly affected areas. But the biggest toll for doctors is the emotional strain of taking care of patients and explaining to their loved ones what will happen.

Ebola damages the human body through its own immune system. When we get sick, our immune cells release cytokines into the bloodstream. These little molecules trigger a multitude of mechanisms to help the immune system, from triggering inflammation to eating up the nasty infected cells hurting us.

When we get sick, viruses target our immune cells. One of our immune cells is the dendritic cell, which acts like an alarm system, gobbling viruses and signaling to its fellow immune cells to make antibodies. Ebola manages to sneak into the dendritic cell and turn its alarm system off. Without dendritic cells warning our immune system about an invading virus, Ebola starts to replicate uninterrupted. From here, Ebola starts to spreads to your major organs and causes massive cell death.

Cells are quite the well-oiled machines. When cells die they usually undergo apoptosis, which is a fancy term to describe organized cell death. Enzymes are triggered to break down the parts of the cell that are required for proper maintenance and the cell begins to shrink. The dying cell communicates that it is about to die and macrophages will clean up the small, shrunken cell. With Ebola, cells undergo necrosis, or unorganized cell death. Cells do not signal their death, so their inner contents just float around. Cleanup is much harder in necrosis, and this inevitable build-up will start to affect the body.

When the immune system realizes what’s happening, it’s often too late. Many cells have undergone necrosis by this point and there’s too much waste to remove. Our immune system has no choice but to use its last resort: the cytokine storm. The cytokine storm is like an SOS the immune system sends out in order to use every tactic to stop the spread of a disease. While a good idea in theory, your blood vessels take the brunt of the attack. Blood vessels become more permeable, making it easier for blood to leak out. This, and the release of nitric oxide, makes for a deadly combination: blood pressure falls and death comes in the form of shock.

According to a Gallup Poll conducted in the past week, one-fifth of Americans are worried about contracting Ebola, higher than the percentage worried about catching the H1N1 virus (otherwise known as Swine Flu) in 2009. While the case of Dr. Brantley had a happy ending, the recent death of a Liberian man treated for Ebola in Dallas has left people worried. Even more unsettling: a nurse in the Dallas hospital that treated the Liberian man has recently tested positive for Ebola.

Should we be worried? No. According to Discovery News, containing Ebola is able to be contained if steps such as early identification, isolation, and disease control are followed. The US also has a rigorous, intensive style of nursing, says an Emory professor who was interviewed by Discovery News. Whereas West Africa is struggling to keep contact with those who may be infected, the US has located anyone who had contact with the recently deceased Liberian man and are watching them through the entire incubation period.

However, just because you can sleep easy doesn’t mean Ebola isn’t terrorizing others. You can donate to Doctors Without Borders who are working tirelessly to contain the outbreak in West Africa.

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