If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Understanding the Ebola virus outbreak

Dr. Rishi Desai is a pediatric infectious disease physician and former epidemiologist with the Centers for Disease Control and Prevention (CDC). Created by Rishi Desai.

Want to join the conversation?

Video transcript

- [Voiceover] So, Ebola virus disease has been on the news and today is September 16th and I just want to mark that on the calendar so we can keep track of kind of where things are as they stand today. And these Western African countries are kind of where we're seeing the disease. Nigeria and Liberia, Sierra Leone, Guinea and also Senegal all combined have more than 4,000 folks that have been sick with Ebola and actually over 2,000 people have died of Ebola. And I just want to contrast that with kind of geographically kind of where we've seen past outbreaks that are big. And when I say big, none of the past outbreaks have even compared with the size of the current outbreak. But also the geography is different. You see, in the past it's been more Central Africa. And so, these are kind of two interesting points about the current outbreak. And while we're talking about Central Africa I thought it would be kind of worth noting where the name of Ebola comes from. Actually there's a river down here in Central Africa back in 1976 there was the first outbreak that we tracked and it was actually named after the Ebola River because that's the region where this was first noticed. So, this current outbreak to understand it in its magnitude I think it's useful to kind of take a little bit of a larger view and understand how it transmits or how it spreads in the natural environment, and usually these guys that I'm kind of shading in green. These guys are thought to be kind of one of the animals out there that may be kind of spreading the disease around. So, fruit bats are one of the culprits that people suspect and they also actually get sick with Ebola. So this one I kind of sketched in green and when they get sick they can spread it to other bats in their bat community. And this becomes then, the community because a natural reservoir. We call this natural reservoir of disease or of virus and this is where it kind of circulates normally. And so, we wouldn't even think about Ebola if it was only affecting bats. Probably wouldn't worry about it too much but what happens that every once in a while it affects a human. And the way that this might happen is let's say this person goes in their front yard and they notice a dead bat or a sick bat and they try to care for it and they might get some blood or stool from that bat on their hand, and they can kind of go into a wound, maybe have a cut or it can go kind of in their mouth or if they rub their eyes or nose. So all of a sudden the virus now has a way into the person and so that's kind of how we think that first person might get sick. And that first person we actually have a special name especially if there's an outbreak and that name is an Index Case. We say that this person is the very first person who got sick with the disease here Ebola. And now looking at our calendar, if this person got sick on the 16th today then their first symptoms are not gonna be today. They're gonna happen in a couple of days all the way through three weeks. So really, kind of a long window in terms of when their first symptoms might happen. It could be this month, it might even be all the way through next month because the seventh of October would be three weeks. And generally, we notice that symptoms happen kind of in this window I'm gonna draw right here. So seven to 10 days. That's when their very first symptoms start to appear. So they're not immediate and the first symptoms are kind of vague. There are things like, you know they might feel a little feverish or they might get like kind of a little headache, maybe some muscle aches. So, kind of just general symptoms, not feeling very well and at this point people think, "Well, you know, maybe it could be anything, "some flu or something." So they don't usually go and try to get medical help. But then what happens is that the virus kind of spreads through the immune system and starts getting into all sorts of different tissues and it can cause problems in their stomach, they might want to vomit or have diarrhea. It can go to their lungs, I'm shading in their lungs. They might you know, start coughing. It can cause rashes, it can cause muscles aches, it can cause redness of the eyes, conjunctivitis we call that. It can also cause inflammation around the brain itself. Meningitis. Or it can cause bleeding of the nose or the mouth, the gums. And in fact, that bleeding is really classic because we think of the virus traveling in the blood and so bleeding is a really important thing to notice because it's very, very transmissible. You know, people can get it from the blood and the word for virus in the blood is kind of viremic virus, virus. In this case, it's the Ebola virus, and emic means in the blood. So when the virus is in the blood we would say they're viremic and at this point they might say, "Well, you know, I want to go "and get the help of a doctor." And so, if they go to get medical help the kinds of things that they usually would get would be like IV fluids if they're dehydrated. If they're having difficulty let's say breathing they might get some oxygen. If their blood pressure is low they might get some medications to help their blood pressure kind of come back up to normal. So these are the kind of things that people do and you know, in Western Africa they have all these support out there. You know, they have medical tents setup to kind of help people that have Ebola and so all the care they're giving is considered supportive care. And there's no real specific anti-Ebola medication. Again, we're here on September 16th and people are researching it. But at the moment there is really just supportive care to help people that are sick and nothing specific that targets the virus. Now the worrisome thing, this is now just a... I want you to just kind of wrap your head around this is that with supportive care, what we're seeing in this outbreak on average is a 50% or so fatality rate. Meaning, for two people with Ebola one will die. I mean it's a flip of a coin which is frightening. I mean, if you come down with the symptoms and you're waiting to find out if you have Ebola or not or if you just found out, it's a really, really scary proposition that half of the people with this diagnosis are gonna die. And that's exactly the reason why the world is kind of watching and intervening and helping to make sure that we get this under control. So, in addition to the supportive care the other big area that we kind of think about is how do you avoid transmitting the virus from one person to another. So let me just sketch in a second person here. So here I've drawn a second person and the question becomes how does Ebola get from the first person to the second person? How exactly does it move? And the quick answer is that it moves through bodily fluids. So bodily fluids include everything from blood to vomit and diarrhea or stool and these are kind of the big ones especially blood. Very, very infectious. But also stool and vomit because a lot of these patients are sick and bodily fluids can also be things like saliva and sweat. But again, these first few that I've kind of written out are the ones to really keep in mind, and blood in fact is an interesting one. There was a study that I think is pretty cool and kind of illustrates the point where they showed that one drop. Just one drop of blood from a monkey that had Ebola was enough to carry with it a million little Ebola virus particles and that was thought to be enough to infect a million monkeys. So kind of the idea that one single drop could be enough to really decimate a population. So it kind of drives on the point that if there's a drop of blood, just a single drop or another bodily fluid that really gets over, let's say over into this person's hand and they can kind of go from there to if they touch their face. They can get entry into their body or through their nose or eyes or mouth or let's say they have a little cut. It could actually make its way into the blood through that cut. So, a few kind of interesting ways that bodily fluid can travel but really then it gets a ticket into the second person and the second person can get sick. And of course that could happen with stool or vomit as well. Now another question that I think a lot of people ask is what about airborne? You know, can you breathe this stuff in? And that's a big question and the idea I think is literally is it kind of floating in the air? And the answer is no. You know, it's not really like other viruses like measles and some other ones where it's airborne. So let me just cross that out so it's very clear. It is not airborne. In fact, I think a lot of the confusion comes when you think about things like sneezes. So with a sneeze you can imagine like kind of you know, we've all seen those sneezes or had those sneezes where kind of a big droplet of goo or mucus kind of goes out, and you get this kind of shower, right, of droplets and this kind of right around where you're standing. Just right in your immediate vicinity and that's not gonna affect anyone that's kind of standing away from you, and you could imagine maybe in kind of a strange scenario. Let's say there's a person kind of hanging out right here right next to somebody's shoulder and they're just kind of sitting there. They might get hit in the face with one of these droplets and maybe then you could say, "Well, you know, therefore they got hit "and they're sick with Ebola." But again, it's the droplet which is a bodily fluid and not the fact they were just breathing you know, air like someone that was standing away. So that's not a typical scenario and that's why we don't call this airborne. One quick thing I should mention is that you can get virus that kind of hits a surface and if it hits a surface like a table or the floor, it can actually survive on that surface they think for days to weeks. And so it is an important point because then that means that if someone's been in the room you really have to decontaminate that area and get rid of all those little dried up droplets that are sitting on the surface to make sure that that room is actually really quite clean again. So what it boils down to is that the real way to kind of prevent the spread of this disease is to make sure that these folks are isolated if they are sick with the illness and over here all the caretakers they should be wearing protective clothing. They should be wearing gloves you know, to make sure that they don't get blood on their hands. They should be wearing gowns to cover up the rest of their body so that they don't expose any kind of wounds or cuts or anything like that. They should be also protecting their mouth with a mask and goggles as well. And so, this is actually exactly in the nose. So all these should be kind of covered up. And so, even working in these conditions can be really tough. I mean, these full body suits can get very, very hot and it can very, very difficult to work on these conditions. But this is really what you want to see to isolate Ebola from one person not getting to another and in addition to just hospital workers, of course you also have to remember the fact that it's gonna be you know, funeral directors that are working with dead bodies which can actually again spread virus. Believe it or not, a dead body can actually spread for weeks after the person has died. It can be lab workers that are dealing with specimens or family members actually are huge. So, all these different people at risk and by doing this, you basically prevent the virus from spreading and hopefully end this scourge that's happened in Western Africa.