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TB epidemiology

Find out how many lives are affected by TB around the world. Rishi is a pediatric infectious disease physician and works at Khan Academy. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Stanford School of Medicine.

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Video transcript

Voiceover: Back in 2011, I'm going to write it down here. Our worlds population was about 6.9 billion. That's a pretty large number and sometimes when I'm thinking of big numbers they all kind of melt into each other. I thought it would be helpful to just write it out so you could see it. 6.9 billion people and that's what I try to represent here with this little black circles, that's my best attempt. It's showing all the people on the planet and you just have to take my word for it that it's roughly representative. What I wanted to point out is that the WHO, the World Health Organization, has said that about one in three people living on our planet, so you just divide this number by three. One in three people has latent TB infection., so this is an enormous number of people. When you read that you might not think about it but that's actually 2.3 billion people with latent TB infection. Remember when I say latent TB infection, what I mean is that the bacteria is either dormant inside of someone's lungs or it's dead but it's really hard to tell the difference so we always kind of hedge on the side of being cautious and we treat them as if they have dormant bacteria in their lungs. Some of us might even see the term LTBI. Now keep your eye on the map and what I'm going to do is show you what that would actually look like. So if I actually erased two-thirds of the people this is what you basically have left, something like this. This people are the ones that we can imagine then have latent TB infection. Still a lot of people right? The WHO found that in 2011. There are also about nine million individuals that had active disease. This is actually people that are coughing and having chest pain, maybe having bloody sputum, all sorts of signs and symptoms of active disease. That's a huge number of people and we know that a lot of those folks have active disease, they're actually coming from this pool of latent TB infection. Now about 10% of these folks that have latent TB infection will actually go on to get active disease and you can break that down further and say well 5% will be in the first couple of years after they get the latent TB infection. Another 5% will be over a lifetime, will be in there lifetime. You can split it up so you can see that most of that risk, that 10% risk is coming in the first couple of years. In general if you think about 10% of that enormous number, 2.3 billion that's a lot of sick folks, right? Let me actually draw in here what 10% of these people would look like just so you get a visual idea. Maybe this person in Brazil will be sick, maybe another person out here. Perhaps this person over here, maybe someone in America. Maybe someone in Mexico. We've got five, maybe a Canadian, get six. We got six people over there. Maybe seven, eight, couple in India nine, ten. A couple of folks in China 11, 12, 13, 14, 15, I mean it's a lot of folks, right? 17, 18, maybe a Nigerian, maybe an Ethiopian, something like this. Let me just make sure I did the math right really quick. A couple more, let's just do one here and one there. This is 10%, that's what 10% visually looks like, so you get a sense for how many people are actually going to get sick and have active disease. We know that there are a couple of other groups of folks that are also going to get active disease. Some would be the folks that had primary infection because you can get primary infection then immediately have what we call primary progressive disease. Or you might have secondary infection, right? You might have latent TB infection then you get another person coughing on you and we call that secondary infection. These are the different ways that you might get to be part of that nine million who have active disease but I want to point out that this is a huge pool. This is a large number of people and so many, many, many people are going to contribute to that nine million with active disease. Now you might be thinking, "Wait a second the math doesn't add up." Because if you just take 10% of this enormous number that's actually way more than nine million people so how does that make sense? Just remember this is a risk in a lifetime or in a couple of years and this is actually looking at how many people are sick with active disease in one given year. To extend a little bit further, just want to make a little bit of space. Those folks are going to go on to actually some of them are going to go on to die. You're going to have, in 2011 we had about 1.4 million people that died. Ultimately that's really what we're trying to avoid. We're trying to avoid people dying of TB and we want to avoid people getting active disease because it's a horrible illness, and so you can see why there's such pressure to try to find people that have latent TB infection and really intervene before they actually go on to get sick. The final thing I want to show you is actually another picture, I think you'll find this interesting. This is actually 22 countries where 80% of the disease is. Go on take a look at this map we've got 22 countries in total. This account for 80% of the cases of TB, so this together account for 80%. The majority of the disease in the world is coming from this places, so TB cases. It's actually quite interesting, you can take a look at this and say okay, you can see that you've got some African countries, you've got countries in Asia, and you've got Russia, and you've got Brazil out here. These countries combined make up the majority of where people are sick with TB.