Herpes viruses have been around for thousands of years and are the third most common kinds of viruses behind colds and the flu. The word herpes comes from the Greek for “creep,” so named for sores that seem to crawl over the skin. These microscopic infectious agents use the mechanisms of living cells to replicate copies of themselves in plants, animals, or bacteria.
Herpes means different things to different people. Some people immediately think of cold sores while others think of genital lesions. This is because these viruses cause a number of human diseases. Human disease-causing herpes are numbered 1 through 8.
Human simplex virus type 1 (HSV1)
(HSV1) most commonly causes Herpes labialis, the medical term for cold sores. However, HSV1 can cause a few other diseases as well including:
- Cutaneous herpes (skin)
- Genital herpes (HSV1 can cause genital herpes, though HSV2 is the more common cause)
- Gingivostomatitis (painful mouth ulcers)
- Herpes encephalitis (inflammation of the brain)
- Keratoconjunctivitis (inflammation of the cornea and conjunctiva in the eye)
In people with depressed immune systems, HSV1 can cause esophagitis (inflammation of the esophagus), hepatitis (inflammation of the liver), and pneumonia (inflammation of the lungs). Once an HSV1 infection takes hold, it will usually pass in time but rarely fully clears the body. People with HSV1 can usually expect symptoms from time to time throughout their lives. HSV1 is passed through direct physical contact.
Human simplex virus type 2 (HSV2)
HSV2 cause many of the same diseases as HSV1. While both the simplex viruses can cause both cold sores and genital sores, most often HSV1 is the cause of cold sores and HSV2 affects the genitals. HSV2 is also the main cause of neonatal herpes, a potentially devastating disease that can affect the face, eyes, mouth, skin, and internal organs of newborn babies born to HSV2 infected mothers. The disease is so dreadful in infants and the infection is so common in women (1 in 5 American women carry the herpes virus) that HSV2 is one of the routine, mandatory tests that expectant mothers take. Like HSV1, HSV2 is passed between people through physical contact.
Varicella-zoster virus (HHV-3)
Varicella-zoster (VZV) causes chickenpox and shingles (also called herpes zoster). Chickenpox involves fever and itchy, fluid-filled blisters. It’s usually a childhood disease although adults who didn’t have it as children can also get it. VZV is extremely contagious. It sticks around for about a week. Then the symptoms disappear. However, the virus isn’t permanently gone but rather retreats to lie dormant in a large bundle of nerves called a ganglion. In some people who’ve had VZV, it can reactivate later in life, traveling down the nerve from the ganglion to erupt on the skin as exquisitely painful blisters. Since nerves leaving the ganglion supply a small strip of skin on one side of the body, the lesion forms a wedge-shape that resembles a shingle (hence the name shingles). A vaccine against VZV has greatly reduced the number of cases of chickenpox in children and to some extent of shingles in adults.
Epstein-Barr virus (HHV-4)
Most people in the West know Epstein-Barr virus (EBV) by the disease it causes: infectious mononucleosis or “mono.” Infectious mononucleosis is passed through saliva, which is why it’s often called the kissing disease. However, people who share silverware and glassware can also pass EBV. Infectious mononucleosis causes prolonged fatigue, a sore throat, and swollen lymph nodes. Epstein-Barr virus also cause swelling of the spleen, which makes that organ more prone to rupture. Quite extraordinarily (and thankfully rarely), EBV can also cause a few types of cancer, including nasopharyngeal carcinoma (nose/throat cancer) and Hodgkin’s or Burkitt’s lymphoma (cancer of the lymphatic system).
Cytomegalovirus (CMV) is very common. About two out of three people have been exposed to the virus. We know this because random testing of donated blood finds antibodies against CMV in about two thirds of samples. In otherwise healthy people with intact immune systems, CMV doesn’t usually cause many noticeable problems (other than a “mono” type of disease in some people). However, cytomegalovirus can be particularly destructive in two groups of people, newborns and people with weak immune systems. Newborn CMV can affect various organs such as the spleen, liver, and lungs. In severe cases, babies born with CMV can experience hearing loss, vision loss, and mental retardation. In people with weak immune systems, CMV can cause:
- Colitis (inflammation of the large intestine)
- Myocarditis (inflammation of the heart)
- Nephritis (inflammation of the kidney)
- Pancreatitis (inflammation of the pancreas)
- Retinitis (inflammation in the back of the eye)
Human herpes virus 6 and 7 (HHV-6 and HHV-7)
These two viruses are thought to cause relatively mild human disease compared to the others. However, ongoing research is attributing more (and more severe) diseases to these viruses. Both HHV-6 and HHV-7 are known to cause roseola infantum, a rash common in young children. In almost every case, roseola infantum causes a fever lasting about three days followed by a diffuse rash, both of which go away soon after without problem. HHV-6 may also cause middle ear infections and, in rare cases, encephalitis.
Human herpes Virus 8 (HHV-8)
Epstein-Barr virus isn’t the only human herpes virus that can cause cancer. HHV-8 has been found to be the causative agent in Kaposi’s sarcoma, usually found in people with HIV/AIDS. In addition, Kaposi’s sarcoma may occur in people with cancer, those being treated for cancer, and those taking strong immunosuppressant drugs. HHV-8 does not cause significant or noticeable disease in people with healthy immune systems.
Treatment of herpes often involves antiviral drugs that interrupt cell replication at different viral life cycle stages. Vaccines also prevent some viruses from taking hold. We’ll have more to say about the connection between herpesvirus and chronic Lyme Disease in a subsequent post.
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