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What is herpes?

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. 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 Raja Narayan.

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Video transcript

- [Voiceover] A cold sore on your lips or on your genitals is referred to herpes, I think you might've heard that term before, and it's caused by a virus referred to as the herpes simplex virus. The herpes simplex virus or HSV comes in two flavors. There's HSV1, and there's HSV2. It used to be believed that HSV1 mainly caused oral lesions, so I'll write up here oral, and HSV2 mainly caused genital sores or genital lesions. But more recently, it's been noted that HSV2 can cause oral sores, and HSV1 can cause genital sores as well. And in fact, this type of infection is so common that 90% of Americans are exposed to this by 50 years old. So they're exposed in a variety of ways, which makes herpes simplex virus a sexually transmitted disease, so if we talk about the modes of transmission or how it spreads from one infected person to an uninfected person, that can include sex, which can be oral sex, vaginal sex, or even anal sex. Childbirth is an important mode of transmission as well. If an infected mother has any active sores while she's giving birth, her baby can get exposed to the herpes virus. Or even outside of childbirth, any contact with open sores can cause transmission of the virus. Or if you were to come into contact with the bodily fluid that's infected with HSV in another way, so if you were to share bodily fluids, like a healthcare worker that gets stabbed by a needle that was used to draw blood from a patient that has HSV, that counts as a mode of transmission as well. And we'll talk more about that in a second. Generally, from the first point of infection right here, so I'll write infection, and we'll make this type of timeline right here. It takes about four to seven days before the first sores appear. And once they're there, it takes about 10 days for them to heal up and go away. There are six main symptoms that I'll mention here, and we'll start off here, where you might recognize this is somebody's lips right here, and they've developed a cold sore right there. The technical term for this, because it's caused by herpes, we call it herpes labialis. So for shorthand, I'll denote this triangle to represent the HSV virus. Why don't we take a closer look at this cold sore over here? What you might see are these epithelial cells. So this is an epithelial cell that exists on your lips, and maybe I should also mention labia is a term for lips, so herpes labialis is herpes of the lips even though herpes labialis can occur on your gums, on the insides of your cheeks, or even on the tip of the tongue. So this is a cell of your lips right here. It's this epithelial cell that has this nucleus right here. What can happen is that the herpes simplex virus can approach the cell and get inside. As we'll talk more in detail about it in a separate video, it can start to reproduce itself by directing proteins away from what the cell would usually be using these proteins to fortify its cell membrane, or to grow and survive. So if these proteins are going in the direction of making more of the HSV virus, over time, the cell will die out. Or another thing that could happen, is that white blood cells that are flowing through your bloodstream will discover that something is going awry over here, and start to battle the herpes simplex virus if they can find it, or they'll target the cell that's been hijacked, and initiate a process referred to as apoptosis, which is just the coordinated killing of a specific cell. Doing so will produce a dead cell, and when several of these cells on the lips die, that's what gives us the appearance of a cold sore. A similar thing can happen down here on the genitals, but when it happens there, we refer to it as herpes genitalis, which is termed this way because this is herpes in the genitals, and you can see cold sores happening on the tip of the penis or even along the shaft, or in women, these may occur also on the vulva, the vaginal wall, so I'll just write vagina for now, or even as high up as the cervix. And when these occur, they usher in symptoms such as pain where the lesion is. They may also burn because as I'll mention later, once herpes affects the epithelial cells on the tip of the penis or the vulva, vagina, or even on the skin of the shaft, it'll find its way to a nerve, and try and go dormant in the cell body of a nerve, which can cause a burning as well as an itching sensation. One of the things I mentioned here in our modes of transmission for HSV was sharing bodily fluids, and one of the fears that healthcare workers have is that when they're handling fluids that may be from a patient infected by herpes, they could get stuck by a needle. So this is my attempt at a needle right here, and this is the plunger, you could push to inject or withdraw a fluid. So let's say that we've drawn up some blood that may be from a patient that has HSV, and if a healthcare worker accidentally will get pricked right there while handling this needle poorly, perhaps, then they can get lesions similar to what we saw earlier with herpes genitalis or herpes labialis, but occurring on the finger. And these can occur at the sight of inoculation or the sight of the needle stick, or even regionally close by. And this phenomenon is referred to as herpetic, referring to herpes, herpetic whitlow. All whitlow means is an abscess that occurs near the fingernail or the toenail. Imagine a person with herpetic whitlow or somebody that's been scratching an open sore, accidentally touches their eye, you can spread the herpes simplex virus here, which can cause what's referred to as herpes of the eye. And over time, the herpes infection can cause a type of lesion that occurs over the cornea, and the cornea is the center of the eye right here. Again, this occurs if you have contact with an open sore, and then you touch your eye. So the mode of transmission here can be from your finger to your eye. Another unusual phenomenon that can occur is that if you have a herpes lesion on your lip right here, this virus, and I'll draw the virus right there, wants to go and hang out and become dormant in the cell body of a nearby neuron. In the face, that means it wants to go and hang out in the cell body of this nerve right here. This guy is called the trigeminal nerve. And this nerve allows you to feel sensation or touch on your face, so what happens is that the herpes infection will go and hang out in the cell body of the trigeminal nerve right here until the patient becomes stressed, and then it goes back down in this direction to cause a sore on your lips. One of the unusual things that can happen and realize the trigeminal nerve attaches up to the brain, is that instead of going back down to the lip, the virus could prefer to go up to the brain. And it can cause what's referred to as herpes encephalitis, which is an infection of the brain. And that can cause a variety of things like headache, mental disorders, depression, and even be fatal if left untreated. But this phenomenon is fairly rare, and tends to happen in patients that have a very poor immune system, which is why this happens so rarely even though so many people have been infected with this virus before.