 Ebola has made headlines recently as the largest known Ebola outbreak in history. So we thought we'd let you in on some information about what this virus actually is and what it does. Ebola has been around since 1976, but the current Ebola outbreak is thought to have started in Guinea West Africa in December 2013, when a two-year-old boy died of the virus. His mother, sister and grandmother were later diagnosed with Ebola and died of the disease. For which the virus quickly spread through Guinea to Sierra Leone. But where did the virus come from? The virus can be carried by fruit bats, which are a natural host of the virus and don't get sick from it. It may have crossed to humans through eating an infected bat, pig, or non-human primate such as monkeys. Using genetic information, scientists have shown that there was only a single instance of animal-to-human transmission of the virus. After that, the virus has spread from human to human. So what does the virus actually do? The virus enters the body through mucus surfaces such as the mouth, digestive tract, breaks in the skin, or even the inner surface of the eyelid. The virus is surrounded by small proteins that disguise it as a piece of debris. Cells of the immune system that are in charge of cleaning up debris take up the virus thinking they are doing their job. But once inside, the virus removes its disguise. It starts taking over the cell's machinery and produces more of pieces of virus, which get assembled and continue infecting as the cell dies. But that's not all. In addition to disguising itself to get into the cell, the Ebola virus also blocks the ability of the infected cell to tell other cells it's infected. Including the infected cell as a healthy one. These infected cells, macrophages, and dendritic cells are the ones that are supposed to identify the virus and trigger an alarm to kill it. But their function has been subverted to the virus's commands. In this first stage of infection, Ebola builds up an army of viruses without much detection from the immune system. It's a terrible but very ingenious move. When enough virus is being produced, the body starts noticing that something is not quite right and produces inflammatory molecules to alert other cells. But the virus has already done lots of damage to the immune system and the inflammatory molecules damage tissues and cause fevers. Next, the virus infects cells that lie in blood vessels. As the cells die, blood vessels become compromised and blood leaks out, causing internal bleeding. This gives the virus an opportunity to travel in the blood to other sites in the body, usually the liver, spleen, and digestive tract. There, it infects even more immune and blood vessel cells, which in combination with the inflammation and damaged blood vessels leads to loss of organ function, fevers, and blood pressure instability and shock. Because the virus is present everywhere in the body, the body's immune system produces even more inflammatory factors, which leads to what we call a cytokine storm, followed by sepsis and sometimes death within a few weeks of infection. Because the virus first infects the very cells that are supposed to detect and kill it, it can evade a large part of the immune system, which is why it's so lethal. However, it's been very interesting to look at the 45% of patients that survive the disease. These patients have a few things in common. Number one, they developed an immune response early on in an infection. And number two, the immune response was short-lived, with both pro and anti-inflammatory factors. Instead, those that die from the disease had a delayed immune response that was only pro-inflammatory, leading to the cytokine storm, which kills the patient. The Ebola virus is present in bodily fluids, such as blood, urine, and sweat. Contact with an infected person's bodily fluids after symptoms appear is the only way to become infected with Ebola. Ebola cannot survive while floating in the air, as the flu virus can, so it can't travel very long distances. Because of this, Ebola is hard to contract unless you are working directly with a patient's bodily fluids. Viruses are now keeping a close eye on the Ebola virus's genetic material to determine if it is changing or evolving over time. We do this for a few reasons. One, we want to make sure it doesn't change so much that we can no longer diagnose an infection. And two, we want to understand if the virus is becoming more or less infectious. In fact, if the virus became less deadly, it may even spread more quickly, as people will be transmitting the virus for longer. Currently, there are treatments in clinical trials to combat the virus. These include vaccines that contain pieces of the virus, drugs that block the virus from entering cells, block the Ebola proteins once the virus enters the cell, or block the ability of the virus to make copies of itself. These are only a few of the current treatments being tested for Ebola. It's fascinating to see just how ingeniously viruses evade our natural defenses and spread so quickly, thanks to millions of years of evolution. The most important thing to keep in mind in the war against Ebola is to be just as ingenious by monitoring its every move at the genetic and at the population level. This video has been produced by Eureka Science. To stay in touch with Eureka Science, like us on Facebook, follow us on Twitter, or subscribe to our YouTube channel, or visit us at Eurekascience.org. Thank you for watching!