Herpes viruses are some of the most common viral infections that people experience. They also have the incredible property of dormancy and recurrence that makes them different than nearly all other viruses.
The word herpes comes from the Greek word that means to creep, or to spread slowly. The Latin word for the same is serpere, from which the word serpent comes from. Another English word from the same Greek root is herpetology which is the study of amphibians and reptiles, including snakes.
The family of viruses called the herpes viruses, likely got the name herpes from the creepy nature of the rashes it often causes.
Some Famous Herpes Viruses
The herpes family of viruses include some of the most familiar of all viruses. The following is a partial list of diseases caused by herpes viruses:
- Oral herpes primary infection and its recurrent state, cold sores or fever blisters
- Chickenpox and its recurrent state, shingles
- Genital primary herpes infection and its recurrent state, genital herpes
- Mono caused by EBV and CMV
- Roseola, which may have a recurrent state called pittyriasis rosea
As you can see, the herpes viruses cause many very familiar illnesses, and many of them have very familiar recurrence patterns.
We may be familiar with the fact that cold sores can happen over and over, or that shingles can be a repeating event in one’s life, but it is worth noting how unusual this experience is for viruses. Nearly all viruses come and go, leaving you immune from ever being infected with that virus again. Think about having the most common viral infection of them all, a cold. Let’s say your cold is from the most common of all cold viruses, the rhinovirus, and this cold is from rhinovirus type #128. Well, the rhinovirus #128 that is causing your cold landed in your nose a few days ago, and then grew in your nose, throat and lungs for a few days or even a week or two, then you body killed every last trace of rhinovirus #128 and your nose, throat, and lungs healed completely. After a few weeks, there is no longer any trace of rhinovirus #128 in your body. Further, you now make antibody to this virus, and if it ever lands in your nose again, it will fail to grow there, you will never have a rhinovirus #128 infection again.
That’s how nearly all viruses work. They land, they infect, they are utterly destroyed, and they never infect again.
The Permanence and Recurrence of Herpes Viruses
Herpes viruses do not infect us only once, and only for a short time. The most curious aspect to the life of herpes viruses is that once they enter our bodies, they never leave. The body attacks the virus, like all viruses, and clears the infection, but the herpes viruses are not cleared fully, they retreat into a hiding place, and sit in our bodies, causing no symptoms, for the rest of our lives.
How does a virus accomplish this feat? Where do the herpes viruses go?
To understand how this happens, we need to think again about what is a virus and how they work in general. Readers of Real Answers may remember a post on just such a question, https://www.advancedped.com/what-is-a-virus/. Briefly, a virus is a most curious thing, in some ways living, in some ways not. What it is is a package of information wrapped in proteins that allow the information to be delivered to where it can be copied. The information is genetic. Every virus contains a small strip of DNA or RNA. Either way, this strip of genetic material contains instructions that can command your cell’s genes to stop what they are doing and make a zillion copies of the viruses genes, and its protein coats.
The protein coat is a wrap of proteins that contain the right signals to make your cell ingest the virus and then deliver its genes to your genes. So just imagine, a virus really is simply a bit of information that is wrapped in a delivery system, together the information and its delivery signals allow the whole package to be copied billions and billions of times, destroying your cells and leading to a rapid spread across the part of your body infected. As to if a virus is alive, those who say yes point to the fact it reproduces. Those who say no point to the fact that it uses no energy, can be stored forever, only takes any action when activated to copy itself. Alive or not though, nearly all viruses come and go.
Herpes viruses are highly unusual in this extra step they take. If any herpes virus infects me, it does what all viruses do, it seeks entry to my cells, zeroes in on the nucleus of my cell where my DNA sits, takes over my DNA, and forces my cell to make zillions of copies, destroying that cell, and spreading all over neighboring cells. Like all other viruses, this sequence goes on and on until my immune system attacks the virus by destroying every one of my cells harboring one.
Now, here is where it gets different. Usually my immune system will clear every last trace of the infecting virus. But in the case of herpes viruses, once under attack, when so many of my cells containing the virus are being destroyed, the herpes virus will enter a certain type of cell and stop copying itself. It will lie inactive in that cell, meaning its DNA will sit somewhere in my cell, no longer demanding my cell copy it or its protein shell. If the DNA sits in my cell quietly, causing no disruption, my immune system will no longer be able to notice it is there. The cell it sits in will not be bothered in any way and will keep functioning as if no virus is present.
As a result, two things happen. First, all my symptoms cease. No cell destruction, no cell disruption, no further attacks of my immune system against the herpes virus means no fever, no rash, no pain, no symptoms at all. Second, the herpes virus now sits in a set of cells in my body forever. At any time that bit of herpes DNA can re-activate however, and start the infection situation over again. At that time, symptoms reappear, usually in the form of a rash in a patch or spot where the virus was hiding. During recurrence, I would not get as sick as the first round, because I have my antibodies against that herpes virus to prevent a full out infection, but an infection can erupt in a small area of my body, until my immune system beats the outbreak back into dormant hiding.
An Example: Chickenpox- how the virus goes dormant
Chickenpox is a great example of herpes virus infection, it has all the features noted above. Many people don’t know that chickenpox virus is a herpes virus, but it really is. Many people are familiar with the fact there are oral herpes and genital herpes infections. Well, chickenpox is just like those, but occurs on the body, one could accurately consider it body herpes.
If you think about a typical case of chickenpox, what happens is that the chickenpox virus enters your body, almost always through the nose, throat and lungs. Once in the cells lining the airways, it spreads to the lymph nodes next to the airways and infects these lymph node cells for 2-4 days. Then the zillions of copies of this virus burst out of the lymph nodes, travel in our blood to our liver, spleen, and other major collections of immune system cells. Now the chickenpox virus copies itself in these parts of our body for another week or so, then bursting in huge numbers into our bloodstream once again, but this time the virus causes us to have fever and hundreds of spots of redness in our skin that turn into tiny yellow fluid-filled blisters that then scab, a situation we call chickenpox. At this point the virus also infects our lungs, and as the virus is copied there, it is released into our breath, allowing us to spread it via the air to anyone around us.
Notice that the chickenpox virus starts out its infection in our lymph nodes, then other structures of our immune system. This low level infection usually causes few symptoms, at least initially. This is how an incubation period works. The virus is in me, but I don’t feel it yet, so I don’t know I am sick, I am incubating the virus, but symptoms only happen when enough cells are destroyed for me to notice. In this case, the illness appears once fever happens, and the rash from visible skin cells being under attack.
Now, when my body tries to wipe out the chickenpox virus, this virus finds nearby nerve cells, enters the nerve cells, a very specific type of nerve cell. The cell the chickenpox virus seeks and hides in is called the cell of the sensory ganglia. Think about how the nervous system works. There are nerves that take signals from the brain and spinal cord and deliver those signals to muscles of the body. These are the action, or motor nerves. And there are nerves that take information from the body and deliver that information to the spinal cord and brain, these are the sensory nerves. Now think about a stripe of your body, say a few inch wide band of your chest. All the touch and pain and temperature nerves in that band of skin gather together into large fibers of nerves that culminate in a clump of nerve cells on the back of the spinal cord. That clump of cells is called a ganglion, and since it is a clump of sensory nerves, it is called a sensory ganglion. Now, since this ganglion is located on the back, not front, side of the spinal cord, it is called the ventral sensory ganglion. Many of them are the ventral sensory ganglia. One more fact about nerves. The nerve cells can be very, very long. One cell, the motor nerve to the toes, starts in a clump of cells in the spinal cord, where most of that nerve cell resides, but that one cell creates an extension of that one cell that looks like a very long, very tiny thread, that goes from your spinal cord to your toe!
So when the chickenpox virus comes under attack, as my immune system tries to clear every trace of these viruses from my body, the chickenpox virus finds a nerve fiber belonging to a cell whose main body sits in a ventral sensory ganglion. Once it enters the nerve fiber, the virus travels back up that fiber to enter the nucleus of that nerve cell that sits on the back of the spinal cord just where the cells, that sense for that band of skin, sit on the spinal cord. Once in the nucleus, the chickenpox virus makes an average of 7 copies of its DNA, forms it into a circle of chickenpox virus DNA that then sits next to your nerve cell DNA for the rest of your life. Curiously, this ring of chickenpox virus DNA does create some signal that keeps that nerve cell from ever dying, helping make its presence permanent for the life of the person. The chickenpox virus can get to the nucleus of the ventral sensory ganglion either by climbing up the nerve cells’ long fiber, or directly via blood servicing the nerve cell.
For most people, that is the end of the story, the 7 copies of chickenpox virus DNA simply sit in the nerve cell nucleus, causing no symptoms. No one can feel it being there.
But sometimes the copies of chickenpox virus reactivate.
Example of herpesvirus activation: Shingles
In the days before the chickenpox vaccine, about 1 in 5 people would experience their dormant chickenpox virus coming back into action, or reactivating. The way that works is that the long dormant chickenpox virus DNA, sitting quietly in your dorsal sensory ganglion of your spinal cord, starts copying itself, making zillions of new chickenpox viruses once again.
These viruses travel down the fiber of that nerve cell in the spinal cord, and then burst out the tips of those fibers, which are in your skin. The patch of skin where those fibers end develops the typical rash of chickenpox, but only in the area of the tips of those infected nerves. Since the rash of reactivated chickenpox only happens in these patches, it is called shingles, looking like a shingle of rash.
The immune systems comes to the rescue once more, beating back the chickenpox re-invasion, and the chickenpox virus once again goes into hiding, back to the nucleus of the sensory dorsal ganglion, where about 7 copies of the chickenpox virus DNA form a circle of DNA that sits quietly, no longer noticeable, for the rest of that person’s life, until the next reactivation.
These recurrences can be far more painful than the first chickenpox infection because the cell inflamed is the nerve, and not just any nerve, but the sensory nerve, the source of sensations like pain.
Chickenpox v. other herpes infections
The main difference between chickenpox and oral and genital herpes, is that the chickenpox virus attacks the whole body, and goes dormant in the sensory ganglia of cells going from the lower tip of the spinal cord all the way up to the sensory ganglia of the head and brain. Oral herpes only attacks and stays dormant in the ganglia of the mouth. Genital herpes only attacks and goes dormant in the ganglia of the genital skin. Both only then recur in their specific regions. But chickenpox virus can recur anywhere on the body, the patch can be on the torso, or face, or any patch of skin.
In the case of roseola, we are not sure where that herpes virus goes dormant, but in white blood cells, including some of these cells in the brain. An unusual rash called pittyriasis rosea, which is a burst of red bumps on the torso in the shape of a Christmas tree on the back, is thought by some to be the result of roseola virus reactivation.
The main virus causing mono, the Epstein-Barr virus (EBV), goes dormant in a certain type of white blood cell, called the B-cell. B-cells are the immune system cell that make all our antibodies. Once you get over mono, the EBV sits dormant in about 1-50 in a billion of your B-cells, sitting there the rest of your life. Like all herpes infections, EBV reactivate, but when they do, all that usually happens is that bursts of virus appear in your saliva, making you contagious, but not at all ill.
Lastly, there is the widespread, but usually harmless, herpesvirus called CMV. After you are born, if you get a CMV infection, usually no symptoms occur, you don’t get sick. By age 80, about 90% of humanity has had this infection. But for some people, the first infection causes a full blown case of mono, with fever, sore throat, and big lymph nodes. Like all herpes viruses, CMV goes dormant, and its cell of choice to hide in are the cells of the bone marrow that make tissue based white blood cells. It can reactivate too, but almost always there is no illness associated with reactivation of CMV in healthy people. CMV causes its greatest harms if it infects a fetus or a person with a damaged immune system.
A last word on chickenpox, and it is about the words. Most people call this virus the chickenpox virus, but it goes by a few other names. One is varicella, the other is zoster. If the chickenpox virus is causing a case of chickenpox, it is called the varicella virus, since the medical term for chickenpox is varicella. If it is causing shingles, it is called the zoster virus, since the medical term for shingles is zoster. Many articles refer to the chickenpox virus as the varicella-zoster virus. Most technically, the chickenpox virus is categorized in the herpes family as the human alpha herpes virus 3.
In case you were wondering, this is the numbering system for all herpes viruses:
1- oral herpes
2- genital herpes
4- EBV- the main cause of mono
5- CMV- another cause of mono and other infections as noted above
6- Roseola- the high fever followed by rash infection of infancy, and there may be a herpes virus 7 that causes roseola too.
Preventing Infections with Herpes Viruses
There is only one vaccine for any of all the herpes viruses, it is the chickenpox and shingles vaccine. It contains a different type of chickenpox virus than the virus that causes natural chickenpox. It is a live virus, that once given, copies like regular chickenpox, and then goes dormant in the dorsal sensory ganglia, again just like regular chickenpox.
The chickenpox vaccine we give children contains the same vaccine chickenpox virus as in the shingles vaccine given to adults over age 50. But the childhood version has far fewer copies of the vaccine chickenpox virus.
- The story of the herpes viruses reminds us of the complex story of how viruses work. They are essentially packages of information in a coating that delivers that package to our genes for massive copying.
- Unusually, herpes viruses are not eliminated entirely when you get over an infection with them. Their genetic material enters into dormancy. Each herpes virus has a select type of cell where it parks its DNA and sits there without causing any illness for the rest of our lives.
- Occasionally, the dormant herpes DNA reactivates and starts dividing again. Many herpes viruses when they reactivate can cause highly localized patches of symptoms.
- So are, we have only one vaccine to prevent herpes virus infections, the chickenpox and shingles vaccines.
We hope this tour of the world of the herpes viruses was of interest. They do creep about and so deserve their name which means creeping, but perhaps learning a bit about how they work makes them a little interesting too.
To your health,
Dr. Arthur Lavin