Nine in 10 Americans carry a dormant virus that can reactivate later in life and cause lasting damage to the brain, nerves and organs, according to researchers at the University of Colorado.
The virus, varicella zoster virus (VZV), is a type of herpes virus responsible for chickenpox, shingles and several other common infections. Most people contract it in childhood, when it causes chickenpox, and after recovery it lies dormant in nerve cells for the rest of a person's life.
In a new article, the researchers said that although the vast majority of people carry dormant VZV, the virus remains an underrecognized cause of serious neurological and systemic disease. At least one in three people will experience VZV reactivation at some point in their lives, they said, and when it happens, it can affect sensory nerves, blood vessels and multiple organs, producing what the researchers described as a whole-body spectrum of disease.
Shingles and nerve damage
The most common form of VZV reactivation is shingles, an infection that causes an extremely painful, blistering rash on one side of the body. Shingles typically affects adults over 50 and travels from the spinal cord down nerve pathways throughout the body, causing debilitating nerve pain and damage.
Left untreated, the researchers warned, the pain associated with shingles is a leading cause of suicide among older adults, and patients may suffer facial paralysis that can become permanent.
Reactivation can also cause multi-organ damage to the heart, eyes, lungs and intestines through nerve inflammation, the authors noted. Shingles may also raise the risk of heart attacks, strokes, cognitive decline and dementia, they said.
A virus that hides without a rash
The article, published in Nature Reviews Disease Primers, warned that VZV disease can spread internally without producing a rash or any other visible sign, making it especially difficult to detect.
"VZV is an extraordinarily stealthy virus because it can cause disease in places throughout the body without necessarily announcing its presence with a rash," said Dr Maria Nagel, corresponding author of the article and a professor of neurology and ophthalmology at the University of Colorado Anschutz School of Medicine.
"In my practice, one of the most under recognized manifestations of VZV disease without a rash is zoster sine herpete ('internal shingles'), in which the patient presents with severe, one-sided burning pain with normal imaging studies," Nagel said. "Until the diagnosis of VZV infection is made, the underlying cause of the patient's pain goes untreated."
Chickenpox in childhood
To prevent complications that researchers say can become irreversible, they urged prompt detection and treatment of VZV infection, starting with chickenpox in childhood.
Chickenpox affects about 150,000 children in the United States every year, causing fever, loss of appetite, headache and tiredness alongside its telltale raised red bumps and small fluid-filled blisters.
Cases in the US have fallen sharply over the past 30 years, dropping 97 percent since routine chickenpox vaccination began in 1995. The Centers for Disease Control and Prevention estimates that about 90 percent of US children receive the two-dose vaccine, typically given once between 12 and 15 months of age and again between four and six years. The vaccine is estimated to be between 90 and 98 percent effective.
Diagnosing hidden complications
Shingles most commonly causes a one-sided rash accompanied by sensitivity to touch, fluid-filled blisters, itching, fever, headache, sensitivity to light and fatigue.
But diagnosing other VZV-related conditions is far harder, the researchers said. These include nerve and vascular damage, meningitis, brain swelling known as encephalitis, and Ramsay Hunt syndrome, which causes facial paralysis that can be fatal.
"Doctors need to recognize that VZV neurological and systemic disease can occur without a rash or months after a rash," Nagel said. "When someone presents with a puzzling neurological or systemic condition that affects one side of the body, VZV should be considered as a potential cause, even when there is no obvious evidence of shingles."
Vaccines and research gaps
Both the chickenpox and shingles vaccines have been shown to reduce the risk of developing either disease, the researchers said. The shingles vaccine is given in two doses after age 50, or after age 19 for people with weakened immune systems, and it is estimated to be 90 percent effective.
Despite this, the researchers warned there is still little long-term research into other manifestations of VZV reactivation beyond shingles itself.
"There is a critical shortage of clinicians and researchers who specialize in the neurological and systemic manifestations of VZV," Nagel said. "Recognizing these infections requires an awareness that VZV can behave very differently from the classic picture of shingles."
