Shingles (Herpes Zoster) Viral Disease May Transmit Genetically
Chickenpox (varicella) and shingles (herpes zoster) are distinct diseases caused by the varicella-zoster virus (VZV). The VZV is a herpesvirus. Chickenpox is a highly contagious rash that usually occurs in childhood. It is the manifestation of a primary infection. Shingles is usually a localized, unilateral (occurs on one side of the body) eruption that follows a linear pattern along a nerve. Shingles is a reactivation of a dormant varicella-zoster virus.
Shingles is caused by the varicella-zoster virus (VZV), also known as HHV-3. VZV is genetically similar to the herpes simplex viruses, the type of viruses that causes cold sores and genital herpes. Herpes simplex virus also takes up permanent residence in sensory nerve ganglia, but not in the dorsal root ganglia of the spine, as does VZV. In chicken pox, the virus is inhaled and begins replicating in the upper respiratory tract before spreading to the liver and other body systems.
Shingles, also known as herpes zoster, is caused by the same varicella-zoster virus responsible for the common childhood illness chicken pox. After a person has had chicken pox, the virus stays dormant in the body, but years later can reactivate in spinal nerves and cause shingles.
The herpes virus that causes shingles is an infectious sub-cellular particle. It consists mainly of DNA or RNA: genetic material surrounded by a protein or lipoprotein hull, or "coat." This hull protects the virus and facilitates its replication. In some patients, herpes zoster can reactivate subclinically with pain in a dermatomal distribution without rash. This condition is known as zoster sine herpete and may be more complicated, affecting multiple levels of the nervous system and causing multiple cranial neuropathies, polyneuritis, myelitis, or aseptic meningitis.
Shingles is thought to be caused by the reactivation of the same chickenpox -- causing virus, varicella -- zoster. It is generally a disease of the elderly but can also develop in insulin -- dependent diabetics and those who have immunodeficient diseases such as AIDS and leukemia. A shingles outbreak can be triggered by the stress-emotional or physical-or by certain medications, including steroids [ex: prednisone], chemotherapy and radiation.
Adults with shingles may transmit the virus to children and cause chickenpox. During the latent phase, the virus resides in the dorsal root spinal ganglion or the cranial nerve ganglion. Reactivation from latency, usually during periods of impaired cellular immunity, causes herpes zoster (shingles). Despite being one of the most genetically stable human herpesviruses, nucleotide alterations in the virus genome have been used to classify VZV strains from different geographical regions into distinct clades. Such studies have also provided evidence that, despite pre-existing immunity to VZV, subclinical reinfection and reactivation of reinfecting strains to cause zoster is also occurring.
Shingles tends to run in families, indicating these people may have an increased genetic susceptibility to the viral disease marked by a painful, blistering rash, researchers said recently.
The researchers looked at 1,027 people treated at a clinic in Houston between 1992 and 2005, half of whom had shingles and the other half had skin conditions other than shingles.
Those with shingles were about four times as likely as the others to have had a close family member with the disease. In all, 39.3 percent of the shingles patients had such a relative, compared to 10.5 percent of the other patients.
Doctors have puzzled over why some people get it while others do not. These findings may provide some of the answer.
"Twenty percent of people eventually develop shingles and 80 percent will not, no matter how long they live," Dr. Stephen Tyring of the University of Texas Medical School at Houston, one of the researchers, said in a telephone interview.
"So what's different about those 20 percent? It seems that the familial predisposition, which must translate into a genetic susceptibility, is a significant factor," Tyring said.
The study appeared in the journal Archives of Dermatology four days after the U.S. Centers for Disease Control and Prevention recommended that people 60 and older get Merck & Co Inc's (MRK.N: Quote, Profile, Research) vaccine Zostavax to protect against shingles.
The CDC urged these people to get a single dose of Zostavax, the only vaccine to prevent shingles, even if they had a prior bout of shingles. There is no cure for shingles.
Nearly a million shingles cases are diagnosed each year in the United States alone.
'FIRST IN LINE'
"Since we now have a vaccine to prevent shingles, we can urge those who have had blood relatives with shingles to be first in line to get vaccinated," Tyring said.
Shingles causes a burning, painful skin rash with blisters that can last up to five weeks and pain that can endure for months or years. Left untreated, shingles can cause irreversible nerve damage. The risk for getting shingle rises starting at around age 50, and is highest among the elderly.
Researchers have struggled to understand the cause of the reactivation of the virus, but believe it may be due to stress, an impaired immune system or the effects of aging.
"The genetic propensity in the broadest sense would make reactivation of the virus more likely. But it may also be a genetic propensity to have a lower threshold to stress if stress indeed is a trigger," Tyring said.
Shingles cannot be passed from one person to another. However, the virus that causes shingles, VZV, can be spread from a person with active shingles to a person who has no immunity to the virus by direct contact with the rash, while in the blister phase. The person exposed would then develop chicken pox, not shingles. The virus is not spread through airborne transmission, such as sneezing or coughing. Once the rash has developed crusts, the person is no longer contagious. A person is not infectious before blisters appear or with post-herpetic neuralgia (pain after the rash is gone).
Treatment is generally with antiviral drugs such as aciclovir (Zovirax), famciclovir (Famvir) or valaciclovir (Valtrex). For the antiviral drugs to be effective, patients typically need to begin taking them within 2-3 days of the appearance of the rash. People are less likely to get shingles if they have had the chickenpox vaccine, which was approved by the Food and Drug Administration in 1995. Vaccine: Zostavax, made by Merck, was licensed May 25, 2006 by the Food and Drug Administration (FDA) for use in people 60 years old and older to prevent shingles. This is a one-time vaccination. Zostavax does not treat shingles or post-herpetic neuralgia (pain after the rash is gone) once it develops.