Human Herpesviruses

Human Herpesviruses

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Hundreds of viruses infect humans causing diseases ranging from the common cold to ebola. Herein, the focus is on the herpes family of viruses, which are among the most common infections of mankind. There are eight different members of the herpes family based on our current understanding of this group of viruses that infect humans. These viruses and common diseases they cause (or are suspected to cause) are listed below.

Table: Human Herpesviruses

Herpes simplex virus -1 (HSV-1)              Oral herpes (fever blisters)

Herpes simplex virus -2 (HSV-2)              Genital herpes

Varicella-zoster virus (VZV)        Chickenpox, shingles

Epstein-Barr virus (EBV)               Infectious mononucleosis

Cytomegalovirus (CMV)              “Mono-like” illness, infections in Immune-compromised patients

Human herpesvirus-6 (HHV-6) Roseola, “mono-like” illness, association with multiple sclerosis and chronic fatigue syndrome

Human herpesvirus-7 (HHV-7) “Mono-like” illness, pityriasis rosea

Human herpesvirus-8 (HHV-8) Kaposi’s sarcoma

After primary infection, all the herpes viruses enter a state of latency (dormancy), which occurs in various different cells or tissues (e.g. lymphocytes, epithelial cells, neuronal cells, etc.). Latency is life long. Given the right circumstances, the virus can surface again in its activated form, which is called reactivation. Containment of the primary infection, maintenance of latency, and thus prevention of reactivation is under control of the immune system (see below).

Among the herpes viruses, herpes simplex virus (HSV) has been the most thoroughly studied. This virus has an impressive array of machinery (enzymes, structural proteins, etc.) to induce and maintain infection. The mechanisms by which the virus infects an individual, interacts with the immune system, maintains latency, reactivates, and so on, has been established. Presumably, the other members of the herpes virus family use similar mechanisms.

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Herpes Simplex Viruses (HSV)

Herpes (HSV-1) and (HSV-2), are caused by two different but closely related viruses. Both are very easy to catch, have similar symptoms and can occur on different parts of the body. When the infection is on the mouth, it is referred to as oral herpes. When it is on or near the genital areas, it is referred to as genital herpes. Oral herpes usually shows up on the lips or inside the mouth as a cold sore or fever blister. Cold sores are common in young children. They get them from exposure to active cold sores of adults and other children. Oral herpes in adults is usually a flare up of a childhood infection. Sores usually heal in about two weeks however; the virus stays in the body, even though the sores heal. A flare up may occur at a later date, causing sores to reappear again. Direct contact is all that is needed to pass the virus. Symptoms are more painful and last much longer in women and men with illnesses that weaken the immune system, like leukemia and HIV.

Genital herpes appear as a cluster of blistery sores usually on the vagina, vulva, cervix, penis, or anus. Symptoms may last several weeks, go away, and then return weeks, months, or years later. The first episode of symptoms of an infection of genital herpes is called primary herpes. Touching, kissing, and sexual contact, including vaginal, anal, and oral intercourse spread herpes. It can be passed from one partner to another, or from one part of the body to another. It was once thought that contact with open sores was the only way to get herpes. We now know that it is possible, but less likely, to get herpes from someone at a time when there are no sores.

Varicella Zoster Virus (VZV)

Varicella Zoster Virus (VZV; the chickenpox virus) has many similarities, yet is also different in its mechanisms of disease. Reactivation, which is common in immune compromised host results in zoster (shingles). Such reactivation can occasionally occur in normal patients. Some risk factors for developing shingles include; adults over 50, stress, Hodgkin’s disease, an illness that has lowered resistance, use of immunosuppressive or anti-cancer drugs, spinal surgery or injury, leukemia or lymphoma and other health care conditions. Diagnosis is usually not possible until rash appears. The rash usually clears in 14 to 21 days. The nerve pain may last for another month or longer. In addition to the painful rash, secondary conditions may develop such as, infection in the blisters, chronic pain, (especially in the elderly, that persists for months or years in the sensory nerves where the blisters have been and can be disabling), corneal ulcers and central nervous system infections. Direct contact with Varicella Zoster Virus (VZV) can give a susceptible person chickenpox.

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