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Ebola: At a glance

What is Ebola?
Ebola disease is a life-threatening illness caused by the Ebola virus. In December 2013, a 2-year-old toddler died in a rural village in Guinea, sparking the largest Ebola outbreak the world has ever known (Baize et al., 2014). The outbreak primarily involves three countries in Western Africa: Guinea, Liberia, and Sierra Leone (although there have been additional cases/deaths in other countries). As of early November 2014, there have been over 13,000 cases and almost 5,000 deaths, although experts believe that these numbers could be 250% greater as many patients never seek medical assistance. This outbreak is larger than all previous Ebola outbreaks combined, and the Center for Disease Control (CDC) predicts the disease could spread to other West African countries, infecting over 1 million people by January 2015 (Meltzer et al., 2014)!

The Ebola outbreak is serious because:
  • Previous outbreaks were generally limited to rural villages, but the 2014 outbreak has moved into more densely-populated areas where there is increased opportunity for human-to-human transmission. 
  • There is currently no vaccine or specific medication for Ebola, and the threat of the disease spreading can cause widespread panic around the world.

How does virus replication work?

Many viruses follow the same sequence of events to replicate themselves. In regards to the Ebola virus:
  1. The Ebola virus slips inside of a human immune cell (e.g. macrophage).
  2. The virus turns the cell into a virus factory, assembling a clone army of the Ebola virus. Meanwhile, chemicals that impair the blood’s ability to clot (a condition called thrombocytopenia) are released into the bloodstream. This is what causes the unexplained bleeding in patients.
  3. The cell eventually explodes releasing Ebola viruses that infect nearby healthy cells. The exploding cell sends out chemical signals which seep into the bloodstream and alert the immune  system about the infection. The immune system’s response to the invading virus is what causes the patient’s flu-like symptoms (e.g. fever).

What are the symptoms of Ebola and how is it diagnosed?

It takes between 2 to 21 days (most commonly: 8-10 days) for the Ebola virus to replicate enough to cause symptoms, and initially Ebola can look like a case of a bad flu. To help make things clear, the CDC has listed two key criteria that a patient must meet to raise suspicion of Ebola:
Ebola can cause many other symptoms including weakness, poor appetite, rash, red eyes, hiccups, cough, chest pain, and difficulty breathing/swallowing. On their own, these symptoms do not indicate that a person has Ebola, since they could be caused by a number of things.
If health care professionals suspect Ebola, they’ll order the following blood tests to confirm the diagnosis:
  • Polymerase Chain Reaction (PCR): Looks for viral RNA
  • Enzyme-Linked ImmunoSorbent Assay (ELISA): Looks for anti-viral antibodies

How does Ebola spread?

Ebola is spread when the bodily fluids of a sick patient get inside of a healthy person. These bodily fluids include blood, vomit, feces, urine, saliva, sweat, breast milk, and semen. The virus can survive in bodily fluids that come in contact with surfaces like floors, walls, and handrails for about 24 hours although the chance of infection after a few hours drops significantly (Center for Disease Control, 2014c). Family, friends, and healthcare professionals all care for patients and are at higher risk of coming into contact with the virus. These folks and anyone else at risk (e.g. funeral directors and lab workers) should protect themselves with personal protective equipment, and remove it in the correct order: gloves, then face shield, then gown, and finally mask!
Ebola can also spread through contact with body fluids of infected bats and primates, placing individuals who work with or in close proximity to these animals at a higher risk of contracting the disease.
Once a patient recovers and is symptom-free, he or she is no longer able to transmit the virus. The one exception is transmission through semen, which can transmit Ebola for up to 3 months after infection. Ebola patients are encouraged to abstain from sex during this time. Ebola survivors can go on to have a normal life and are immune to the virus for up to 10 years.
To be clear, Ebola does not spread through the air, through water, or through food, so you can breathe, drink, and eat without worry!

How likely are you to get Ebola?

It’s really useful to know how many people are likely to get infected from a single contagious patient (assuming that nobody gets vaccinated). A number called R₀ (pronounced: R-“not”) allows scientists to rank how contagious a disease is:
  • R₀ of 0 means that nobody will catch the infection
  • R₀ of 1 means that 1 new person will catch the infection
  • R₀ of 5 means that 5 new people will catch the infection, and so on...
In some diseases, a single patient can spread the disease for days (e.g. Ebola) and in others, for decades (e.g. HIV). It turns out that Ebola has an R₀ of 2, which means that a single patient will transmit the virus to an average of 2 other people (unless we intervene). Compare this with one of the most contagious viruses around - Measles, which can travel in the air and spread to an average of 18 people!
Sources: Center for Disease Control & World Health Organization, n.d.; Meltzer et al., 2014; Mills, Robins, & Lipsitch, 2014

How can you treat Ebola?

Unfortunately there is no direct treatment for Ebola (no vaccines or medications) yet. Instead, health care workers provide supportive care, which focuses on keeping the patient alive during the illness while his/her body fights the disease. Supportive care includes:
  • Keeping the patient well hydrated with intravenous fluids
  • Maintaining the patient’s blood pressure
  • Helping the patient breathe, if needed
  • Treating other infections or ailments that come up
Typically people who are likely to survive begin to recover between 6 and 11 days after symptoms initially began. Older patients and those that have more serious symptoms such as bleeding early on in the course of the disease typically die within 6 to 16 days after symptoms initially began (Center for Disease Control, 2014b).

Consider the following:

Why are some countries more affected by Ebola than others? The answer comes down to having an effective public health system. There is a race taking place. On one side, the virus is quickly moving from one person to another. On the other side, the public health team is trying to find and isolate everyone with Ebola so that the virus can’t spread. Speed matters on both sides, and if the public health team can move quicker than the virus, then transmission ends. This requires good surveillance and contact tracing.
  • Surveillance: Some countries have excellent public health systems, and healthcare providers at clinics/hospitals call public health departments about any patient who has an unusual illness or death. Other countries have many rural populations that cannot visit major health facilities because they’re too far away. In these cases community health workers are often sent out, but they sometimes can’t get to every community. As a result, people may get sick and die without the public health team ever learning about it, and the disease can spread far and wide without anyone noticing.
  • Contact tracing: Once a patient is diagnosed with Ebola, the patient is isolated to prevent further chance of spreading the disease. Public health teams then make a list of everyone the patient may have spread the disease to while the patient had symptoms and monitors them for symptoms for 21 days. If one of those people gets sick, the public health team will isolate them and make another list of everyone this new patient may have spread the disease to while this new patient had symptoms. Ideally there should be no one on the list if the public health team works fast enough!
For more information, check out our video on the Ebola outbreak!
Baize, S., Pannetier, D., Oestereich, L., Rieger, T., Koivogui, L., Magassouba, N., … Günther, S. (2014). Emergence of Zaire Ebola Virus Disease in Guinea. New England Journal of Medicine, 371(15), 1418–1425. doi:10.1056/NEJMoa1404505
Center for Disease Control. (2014a). Ebola (ebola virus disease)
Center for Disease Control. (2014b). Ebola virus disease information for clinicians in u.s. healthcare settings
Center for Disease Control. (2014c). Interim Guidance for Environmental Infection Control in Hospitals for Ebola Virus
Center for Diease Control & World Health Organization. (n.d.). History and epidemiology of global smallpox eradication. Smallpox: Disease, Prevention, and Intervention. 16-17.
Meltzer, M., Atkins, C., Santibanez, S., Knust, B., Petersen, B., Ervin, E., … Washington, M. (2014). Estimating the future number of cases in the ebola epidemic - Liberia and serra leon Centers for Disease Control and Prevention. 63(03);1-14.
Mills, C. E., Robins, J. M., & Lipsitch, M. (2004). Transmissibility of 1918 pandemic influenza. Nature, 432(7019), 904–906. doi:10.1038/nature03063

Want to join the conversation?

  • piceratops ultimate style avatar for user Matt
    Is ebola airborne? or just blood borne?
    (12 votes)
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  • leaf green style avatar for user 21ebubeak
    Is Ebola contacted by typing in a keyboard an Ebola patient was previously using?
    (16 votes)
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    • leaf yellow style avatar for user Rishi Desai
      From the author:The virus spreads through bodily fluids, and if a bodily fluid hits a surface, the virus can linger on that surface for days to weeks (viral survival) which is why cleaning of any surfaces (porous and non-porous) is very important. Having said that, the actual chance of an infection is thought to drop within a few hours (viral transmission) after the bodily fluids first come into contact with the surface.
      (33 votes)
  • aqualine ultimate style avatar for user Stuart  Feldman
    So, if you are drinking from someone before they contract the disease, would you have Ebola??
    (6 votes)
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    • purple pi teal style avatar for user Couchsmash
      If by "before they contract the disease" you mean "after they've been infected but before they show symptoms," then yes I suppose there's a small possibility of getting it from their saliva, but if they aren't showing symptoms yet, there hasn't been enough virus replicated yet to really be all over the place. Best not to share drinks in general. :)
      (3 votes)
  • piceratops tree style avatar for user Elizabeth VanHorne
    If you unfortunately had contact with something questionable, say you work in a bank and handled cash or coins from someone that was questionable, would using hand sanitizing liquid be a an effective way to kill the virus on your hands? I know that several people use hand sanitizing liquids during the flu season. Do the same rules apply here?
    (6 votes)
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  • leaf green style avatar for user bhaskar kumar
    what if a person effected with Ebola sneezes is there any chance that it will spread?
    (4 votes)
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    • aqualine tree style avatar for user wagstkod000
      Yes, because if Ebola is in the saliva/mucous propelling from the person's mouth/nostrils(which it probably is), then there is a good chance that Ebola is in your system. (This also depends on the severity of the symptoms of Ebola, how old the person on the receiving end is, how powerful their immune system is, if they already have the virus,
      where the mucous/saliva landed(direct entrance would give you Ebola), and several other factors.) So really, don't be worried. Unless you live in Africa, then you are probably fine.
      (2 votes)
  • duskpin ultimate style avatar for user HarStar
    How fast can it possibly go around?? 8 of my high school teachers went down to the same town in Texas where it is at. The health "professional" said it will be alright if they keep teaching. is that okay!? there is like 200 kids in the high school!! will the government shut down my town because it is so small and soon all of the kids could quiet possibly get sick? or do we have a okay-ish chance of fighting it?
    (3 votes)
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    • hopper happy style avatar for user Ikeda, Miyuki
      Ebola is not airborne, so you, your teachers, and your friends will be just fine. Just make sure not to make any kind of direct contact with someone who feels ill, has a diarrhea, nausea, and all that. You can only get infected by Ebola when the virus actually goes inside your system. The government shouldn't shut down any kind of towns or cities in Texas just because the virus is in there. If you want to fight the virus, you can wash your hands thoroughly, stay off of people with illness, and stay hydrated. (:
      (5 votes)
  • leafers ultimate style avatar for user 59batkiller2
    Strange how the whooping cough is more contagious then Ebola. So is the cause of the whooping more contagious cause its not only able to caught by becoming in direct contact but can also become airborne?
    (3 votes)
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    • piceratops sapling style avatar for user Roste1
      Yes that's correct, airborne viruses are a lot more contagious because simply coughing or sneezing can spread a whole cloud of virus particles in the air, and anyone in close proximity can catch these airborne viruses, and they would not even notice.
      (2 votes)
  • marcimus pink style avatar for user frances
    How about for women survivors, should they never have children since it can spread through the breast milk? Or do they also have to abstain for 3 months (or more)?
    (3 votes)
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  • male robot hal style avatar for user coolchrisdude
    Isn't there a treatment for ebola now?
    (2 votes)
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  • piceratops ultimate style avatar for user Nathan Shapiro
    What specifically is the meaning of an "airborne disease"?
    (2 votes)
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    • male robot johnny style avatar for user jon.email
      Airborne diseases are easily spread between people via the air. Usually it's because the virus infects your lungs, throat, or nose. Often it also makes you sneeze or cough, which helps spray the virus into the air. The virus particles are usually transmitted via tiny droplets that can stay in the air for a long time, so it's likely someone nearby will breathe them in. The viruses often have a shape or design that makes them easier to transmit via air.

      Ebola doesn't specifically target your respiratory system and it doesn't specifically make you sneeze or cough. It's mostly present in your blood and your tissues. It's an aggressive virus that tends to get all over your body, though, so your saliva and sweat tend to have virus particles in them.

      So, if someone in your class had Ebola and was sick, it would be very unlikely that anyone else would get infected: the only way someone else could catch it would be if they got the infected person's body fluids in their face or in a cut (so if the sick person coughed in your face or if you shook hands with the sick person and then rubbed your eye).
      (2 votes)