Stanford School of Medicine
- What is TB?
- TB epidemiology
- TB pathogenesis
- Primary and Secondary TB
- Pulmonary TB
- Extrapulmonary TB (part 1)
- Extrapulmonary TB (Part 2)
- Mantoux test (aka. PPD or TST)
- Interpreting the PPD
- Diagnosing active TB
- Preventing TB transmission
- Preventing TB using the "4 I's"
- Treatment of Active TB
- Drug-resistant TB
- TB and HIV
There are a number of ways that we can help to prevent TB from spreading, learn some of the most common ones. 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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- Can a UVGI cause suntan, sunburn, vitamin D production, skin "aging", skin cancer due to the ultraviolet?(9 votes)
- It can cause all that if one is directly exposed to the radiation, but the system is not (or should not be) meant to operate in and radiate to a place occupied by a human body. Safety depends on how the system is designed, installed and subsequently used.(9 votes)
- Can a pregnant woman transmit TB to her unborn child?(3 votes)
- Yes, the TB germ can be spread from the mother to the fetus via the blood in the umbilical vein or the fetus can contract the TB germ into its respiratory sysytem or digestive system via infected amniotic fluid inside the uterus. My source is a presentation by Dr. Amita Gupta entitled, "Mother to child transmission of TB: what do we know?" from July 19, 2009.(7 votes)
- If "create space" is one of the techniques listed to prevent transmission of TB bacilli from one person to another, why is a fan to circulate air recommended? It seems intuitive to me that the fan would have the potential to blow infected droplet nuclei around the room and thus negate any benefit from creating space between non-infected and infected individuals.(3 votes)
- We're not talking about a fan by the bedside, under the patient's control. As is said in the video at10:15, negative pressure creates a continuous outward current. Clearly the airflow isn't laminate, but you should be able to get closer to the patient without walking into as much of a nasty cloud. That protects everyone in the facility, as long as they don't stand outside by the air vent if the air isn't filtered!(3 votes)
- Let's see:
I know the -cide means killing so we're killing germs and U.V has to do with sunlight.
So....killing germs via sunlight, somehow?(3 votes)
- You're right on. Something interesting about ultraviolet germicidal irradiation is that it doesn't always completely kill the microorganisms that are targeted. The reason behind this is that UV germicidal irradiation only needs to interrupt and break down the DNA of the organism to disrupt vital life processes like homeostasis and reproduction.(1 vote)
- Can TB be prevented by BCG (Bacille Calmette Guerin）？(2 votes)
- BCG immunization is one portion of TB prevention. Dr. Prober and Morgan Theis discuss BCG immunization at8:00into this video: https://www.khanacademy.org/science/health-and-medicine/infectious-diseases/tuberculosis/v/preventing-tb-using-the-4-i-s(2 votes)
- i was a patient in the year 2000. now im fine but when i excited i feel problem to take breath. ANOTHER problem is.. i want to go abroad from my country for job or student visa but in medical report a shadow is seen in my right chest on ex ray report. What can i do? Please give me some advice.(3 votes)
- The best I can give you is get multiple opinions on wether you have latent/dormant/about to be active TB. Go to different doctors or hospitals, and get different opinions. Good luck to you!(1 vote)
- At8:10Sal states the UVGI generator shines out UV light. Isn't it generally a bad idea to indiscriminately irradiate an area with this type of UV light? Did Sal mean a system which might move air through a light tight plenum before returning the air to the room to minimize exposure to, say, people?(1 vote)
- Are there any drawbacks of UVGI? Is it radioactive?(1 vote)
- At1:43, he mentions seeing the live TB bacteria in a smear. Could you diagnose TB this way, or is it not distinguishable enough?(1 vote)
- You say that we have to isolate them especially at night, I am assuming this is because of the night sweats. Why are night sweats worse at night? What is the pathophysiology of night sweats?(1 vote)
Narrator: Let's say you've got two people and one person has Tuberculosis, that's this person over here, I'll call him person A and another person does not, this is person B over here. What are the things that are going to make person A more infectious? What are the things we need to think about, in terms of how likely it is that person B will actually get sick with TB. There are a few things. We know that this person has to actually cough out some TB particles, right? They're going to cough them out and that means that the strength of the cough, let's say they have a real good cough like that, versus a really weak, kind of puny cough, something like that is going to matter. It turns out that the folks that have the strongest cough are the adults. So, any adults, in general, adults are going to have a much stronger cough than children. So, that means that adults are more infectious than children. Let me actually write that as my first key point. It turns out that's exactly right, that we see that in terms of spreading TB, it's the adults that spread it much more than kids and definitely much more than infants. A second point, is that you need live bacteria. This seems obvious that of course you're not going to get anyone sick if you don't have live bacteria. The way to know that someone has live bacteria, you can actually just take some of there sputum or some of their mucus from their lungs and look under a microscope and you would actually see what we call a positive smear. That literally means you smear out the mucus under a microscope and you look with a microscope and you can literally see the TB bacteria. You can also do a culture and see if you can actually grow the bacteria. If you can see the bacteria or grow the bacteria, that's a good indication that there's live TB bacteria there and that's obviously going to make the person more infectious as well. A third point, is if you look in their lungs and you see large cavities, some times you call that cavitary disease, but let me just write cavity here. If you see a cavity there, in that cavity we know is going to be full of little TB bacteria. Those cavities are classic for that and so whenever you see or think about cavities, I want you to remember that the folks that get cavities are the secondary progressive disease folks. Remember there's primary and there's secondary, and it's the secondary progressive disease that causes these cavities. These are the folks that are going to be more infectious because they're loaded with live TB bacteria. What are the things we can do to actually prevent the spread of TB? The first one is actually kind of obvious, it's medication. We have medications that are really good for treating Tuberculosis. One classic thing that we've done is what we call directly observe therapy, DOT, directly observe therapy. All that means is sometimes a physician or a nurse will actually watch a patient take their medications so that they don't forget or sometimes people don't like to take their medications. This is an easy way to make sure that someone's actually taking their medications. We call it DOT. That's obviously going to be helpful for killing off the bacteria, so we don't have to worry about live bacteria anymore. Usually that happens in about two weeks, after two weeks of medications, that usually kills off the bacteria so you no longer have those positive smears and positive cultures. It also helps with symptoms, so if you're not sick with TB you may not be coughing as much. That's another important thing to keep in mind. What else would be important? You could imagine, isolation, making sure the person is actually isolated. So, isolation is key. And specifically you want to make sure they're not around any young people, so definitely don't want them around anyone under the age of four years because, of course, children are really, really susceptible to getting very sick with TB, so you want to make sure they're away from young children and you want to keep them isolated at night. So, at night when they're sleeping - I put a little @ symbol, but at night when they're sleeping you want to make sure that they're isolated and maybe sleeping in their own room. Of course it's ideal if the person is completely isolated, but of course that's not always practical because they might be with their family or their children, but you want to make sure that they're at least away from children under four and at night that they are sleeping alone. Another thing is a surgical mask. A surgical mask is really good because it helps prevent too much of the stuff that's coming out of your mouth to enter the air. Actually, literally, let me just draw it for you. It literally catches a lot of this stuff and prevents it from entering the space around you. This is a mask, let's say a surgical mask, it might hook up like this, maybe like that, and what it does is it literally catches the stuff that's coming out of the mouth and makes it ricochet back in. You can still breath with a surgical mask on, but it just keeps the large particles, maybe large droplets from leaving your mouth. Now, what if you're person B, what's one thing you could do if you're person B? One obvious trick is just standing further away, you don't have to stand so close to person A, you can stand all the way back here. That's going to make it less likely that you're going to get sick with TB. Let me write that here, is create space, create space. Another key idea is, think about what happens when someone passes gas, or there's a horrible smell in a room, what are you going to do? Usually people are going to find the door, maybe they'll open the door and let some air in. This arrow indicates more air coming in. Maybe there's a window here, they're going to open the window and let the breeze come in. Basically do whatever you can to dilute out that horrible smell. If there's a fan, maybe you'll try to turn on the fan and get that spinning. If you can get the fan going that's also going to move around the air. You're just trying to move around the air to get a dilution of that horrible smell. Let me right it out, dilute. The idea here is that you can just literally do simple things. You can open up doors and windows, we call that natural ventilation. You can also turn on a fan to kind of move the air around and you're just trying to dilute out that horrible bacteria so that less of it is likely to enter your lungs. Another thing you can do is actually put on an air purifying respirator. An air purifying respirator is actually a little bit different then the surgical mask. This one is actually going to keep out very tiny, tiny particles. Unlike the surgical mask whick gets the large things, spit and large particles, this one is actually going to capture very tiny particles and it's actually not going to allow them into your breathing area, your airway. It's actually going to make things bounce off, essentially, or get caught inside the filter itself. It wont allow TB particles into your nose or mouth. A common one here, you might have heard of or seen, is called the N95. There are many other types as well, but that's one example of an air purifying respirator. There are a couple more things that you might see that are slightly more expensive, but you might come across them or at least hear about them. One is called ultraviolet, (writing) ultraviolet germicidal. Let's see if you can kind of guess how this works or what it does. (writing) Germicidal, cidal means killing something. Germicidal irradiation, irradiation. A lot of times people will just shorten this whole thing to UVGI. They'll say a UVGI was installed and what UVGI does, it literally takes ultraviolet light and shines it out, and actually if there area couple of TB particles, let's say one here and one here, that UVGI, that irradiation kills that TB particle and X's it out. So, it's no longer alive and the folks in that room are safe. The final thing I want to talk about is called a HEPA filter. It's a filter and if I was to draw the ceiling it would look something like this. Maybe it has some spot on the ceiling where air is flowing in and some spot where air is flowing out. Just erase these parts right here and I'll show you. Let's say that air is coming in this way, let's say three arrows, and you've got air coming out this way, you've got three arrows. So in the middle, somewhere in this area you've got a filter. This filter is going to catch TB particles, so we call it a High Efficiency Particulate Air Filter. (writing) Particulate Air Filter. No one wants to say all of this because it's too long, so just for short, again they say HEPA filter. A HEPA filter is going to then catch some TB particles that are going to flow in and they're going to get stuck in these filters, so coming out on the other side you have nice clean air because the TB particle will not get through that filter. You could even take this a step further. You could say well, how about if we did this and actually, instead of having all of the air returned, let's say we return just part of it and actually allow some of the air to escape outside of our room. Now you have a negative pressure in this room because you have more air leaving the room then is re-entering the room, you have negative pressure, almost like a vacuum because all this air is going up into the filter and not as much is coming back out, so this room becomes negative pressure. There's kind of a vacuum in this room and especially if you do it right. If you close off all these doors and you close these windows, then you definitely create a negative pressure. What that means is that now you can really protect the area around because you close off the door, you close off the window and now there's no way that a TB particle can leave and go into the hallway because if there's a little bit of a gap underneath this door, if that's the only crack in this room, then the negative pressure is going to make air flow through that crack into the room instead of air flowing out into the hallway. That's actually another key trick that they use to prevent TB from spreading, is they'll create a negative pressure where they pump air out, which is what we showed here, and then they'll seal off the whole room, and then the air from the hallway starts entering the room and you can make sure that no TB particles are going to get out into the hallway and get people in the hallway sick.