Herpes zoster, popularly known as the shingles, is an infectious disease caused by the Varicella-Zoster virus, which causes chicken pox (varicella).
Herpes zoster and herpes simplex (labial or genital), although they have similar names and are caused by viruses of the same family, are two completely different diseases.
When we are exposed to the Varicella-Zoster virus for the first time, which usually occurs during childhood, we develop chicken pox, which is a disease characterized by reddish rashes and fever. After a week or two of symptoms, our immune system can control the infection in the skin, causing the disease to heal.
The problem is that this cure of the symptoms is not necessarily a cure for the virus. During the early stage of the chicken pox, the virus invades the nerve endings of the skin and migrates to some chains of ganglia located near the spinal cord and brain, thus being able to "hide" from the immune system for periods that can last for decades. The patient, therefore, cures from chickenpox, but remains infected with the Varicella-Zoster virus for the rest of his life.
Usually this is not a problem, because every time the virus tries to escape from its hiding place in the nervous ganglia, our immune system, which now has specific antibodies against the Varicella-Zoster virus, can prevent it. The patient keeps the virus trapped, presenting no symptoms, nor being able to transmit it to others.
So if we can not get rid of the virus from one side, on the other, our immune system is competent enough to keep it from attacking us again.
However, our battle with Varicella-Zoster depends on a strong immune system. The virus may linger for decades, waiting for a vacillation of antibodies to multiply again. This means that a drop in our immunity is enough for the virus to manifest itself again. Reactivation of Varicella-Zoster does not cause a new picture of chickenpox, but rather a different disease, which is called herpes zoster.
When the virus reactivates itself, it does the opposite way, traveling from the nerve back to the skin, which causes typical herpes zoster lesions, which are multiple reddish vesicles (blisters), restricted to a small area of the body, which is exactly the one that is innervated by the nerves that "hid" the virus.
The way that herpes zoster lesions cluster, usually in a "range" and never surpassing the midline of the body, is the most important characteristic for the diagnosis of the infection. To understand why the herpes zoster injury has this behavior you need to know a little bit about the anatomy of the spinal cord and your nerves. Let's explain in a simple way.
The spinal cord is connected to the brain, is about 45 cm long and lies inside the spine. It goes from the first cervical vertebra, over the neck, to the second lumbar vertebra. Along the medulla are several plexuses of peripheral nerves for the whole body, responsible for the innervation of specific regions.
Each region of the body that receives a branch of nerves from the marrow is called the dermatome. Each vertebra launches a pair of nerves, each innervating a half of the body. The region of the left and right nipple, for example, are innervated by a pair of nerves that is born at the height of the 4th thoracic spine vertebra (T4). The navel region is innervated by nerves that arise at the 10th thoracic vertebra (T10).
Therefore, if the Varicella-Zoster virus is hidden in nodes near the nerve root to the left of the T10 vertebra, for example, when it reactivates, it travels to the navel region and causes eruptions in a band of the abdomen to the left of the belly button.
In the photo to the side, it is possible to see a herpes zoster lesion affecting the region innervated by T1 and T2. Notice that the injury is "in range" and ends exactly in the middle of the body, since only a couple of the nerve usually carries the virus.
The dermatome affected by shingles usually has a burning or tingling sensation for a day or two before the lesions arise. Also common are general symptoms of a virus, such as fever and malaise.
When shingles appears, it usually starts as a very painful and reddish rash, evolving rapidly into the typical blisters. The thoracic, abdominal and lumbar regions are the most affected.
New vesicles erupt over 3 to 5 days, usually relieving after 7 to 10 days, when the blisters dry out and begin to form crusts. Lesions and pain can take up to a month to disappear completely; in some cases, the zoster injury leaves a scar.
Unlike chicken pox, which only appears once in a lifetime, shingles can recur whenever there is a drop in the patient's immunity.
Post-herpetic neuralgia is a complication characterized by the persistence of pain at the affected site, even after a long time of resolution of the lesion. The infection goes away, but the pain stays. In some cases, the pain of post-herpetic neuralgia is so intense and continuous that it can lead the patient to depression and physical disability.
Usually, herpes zoster is self-limiting and affects a small region of the body, usually only a dermatome. If new blisters are still emerging after 7 to 10 days or if the condition is affecting several dermatomes at the same time, one should think about the possibility of a debilitating immune system disease, such as cancer or AIDS. These are the patients at greatest risk for complications.
Reactivation of zoster on the face can be dangerous, especially if it affects the eye area, which can lead to loss of vision. Ramsey Hunt syndrome is a facial paralysis caused by the involvement of the facial nerves by herpes zoster. Also common in this syndrome is the occurrence of labyrinthitis.
The active zoster patient is contagious only to people who have never had chickenpox, ie, those who have never been infected with the Varicella-Zoster virus . Anyone who has never had chicken pox if they come in contact with a patient with shingles will develop chicken pox and not herpes zoster, since the former is always the initial form of contamination by this virus.
No one develops shingles without first having chicken pox. If you have a shingles and you think you've never had chickenpox in childhood, chances are your chickenpox has been so mild that it has gone unnoticed or been mistaken for any other common virus. The fact is that to have herpes zoster, you need to already have the Varicella-Zoster virus hidden in the nervous system.
People who have had chickenpox over a lifetime or who have been vaccinated against the virus may have contact with patients with herpes zoster without risk of developing any disease, as this is a group that has antibodies against the Varicella-Zoster virus.
As already mentioned, to have shingles it is necessary to have had chickenpox at some point in life. Up to 20% of patients with a history of chicken pox in childhood will have at least one episode of shingles, usually after the age of 50. Among patients over 85, this rate rises to more than 50%.
Herpes zoster arises when there is a drop in immune defenses. Among the risk factors we can mention:
Herpes zoster, in most cases, disappears spontaneously after a few days. However, antiviral treatment, such as Aciclovir, Valaciclovir or Famciclovir, is indicated to accelerate this process. These antivirals are drugs that, if started early, preferably within the first 72 hours of illness, decrease the severity, duration, and risk of herpes zoster complications.
In some patients, herpes zoster pain may be severe, and analgesic use is indicated. There are patients the pain is so intense that we need to use opioids (derived from morphine) to control pain. As pain is of neurological origin, antidepressant medications, such as Amitriptyline or Nortriptyline, or anticonvulsants, such as Gabapentin or Pregabalin, may also be used to relieve symptoms, especially in cases of post-herpetic neuralgia.
In recent years, vaccination of children against chickenpox (varicella) has been adopted in many countries and has raised the hypothesis that it is also effective against shingles.
Recent studies have shown that the vaccine is effective in the population over 50 and reduces the risk of a shingles episode by up to 70%. In addition to being effective in prevention, patients who even get vaccinated end up developing herpes zoster have a much lower complication rate than the non-immunized population. Therefore, in addition to preventing it, it also reduces the incidence of complications, immunization with the varicella zoster vaccine can be used in people over 50 years of age, even if they have had chicken pox or even herpes zoster at some point in their life.
Caution: the vaccine against shingles, like any other vaccine, serves to prevent disease, not for treatment.
