|
Shingles (Varicella-Zoster
Virus)
By
Dr. Virginia
Cummings |
Question: I
recently developed a rash on my back and my doctor told me
it was shingles. What is shingles? How did I catch it and is
it contagious?
Answer: Shingles is the common name for an infection
produced by the Varicella-Zoster virus. This is the virus
that produces chickenpox. When a person gets chickenpox,
which usually occurs in childhood or adolescence, the virus
never leaves the body. After recovery from chickenpox, the
virus takes up residence in one of the dorsal nerve roots
that run out of the spinal cord. A pair of nerve roots exit
each spinal vertebra (or backbone), one on either side, and
each nerve root corresponds to a section of the body on that
side.
All of the nerves in that section of the body on that
particular side have their origin in that nerve root. The
section of the body corresponding to a particular nerve root
is called a dermatome. It is shaped like a half-ring,
running around the body from the spine to the midline in the
front.
After an episode of chickenpox, the Varicella-Zoster (VZV)
virus migrates to a nerve root and lies dormant there. The
choice of nerve root is somewhat random, but VZV usually
picks a cervical (neck) or thoracic (trunk) nerve root. It
lives in there, hidden from the body’s immune system, which
has made antibodies and special immune cells against VZV.
These immunities prevent us from ever being re-infected with
VZV (and getting chickenpox again), but cannot eradicate the
virus hidden in the nerve root.
If the immune system ever “relaxes its guard” against VZV,
the virus may reactivate and cause an episode of shingles.
The reactivated virus spreads along the dermatome of the
nerve root in which it was hidden, causing a red inflamed
rash with blisters, like chickenpox, but only in that one
area of the body.
The rest of the body remains unaffected. This rash is unique
to shingles, it is restricted to one side of the body only.
Other rashes affect both sides of the body. Shingles will
only be present in that one ring shaped dermatome.
We often don’t know what caused the immune system to relax
and allow VZV to reactivate. Age is the most common factor -
shingles is rarely seen before age 50. We know that the
immune system becomes less effective with age, and this
decline may be enough to allow VZV to reactivate. Other
things that suppress the immune system, such as medication,
infection, cancer and autoimmune disease, can also lead to
reactivation of VZV.
Just like chickenpox, shingles is contagious. This is a
little confusing. We “catch” chickenpox from someone else,
but we don’t “catch” shingles from someone else - shingles
occur when our immune system “lets down its guard” and VZV
reactivates. In order to get shingles, you must have had
chickenpox already.
The virus enters our body when you get chickenpox and stays
there in a nerve root, waiting to reactivate. However, a
person with shingles can give VZV to someone who has never
been infected with VZV. This first exposure to VZV will not
cause shingles, but rather chickenpox. The good news is that
once you have had chickenpox, you build up immunity and
cannot get chickenpox again, even after exposure to others
with chickenpox or shingles. And exposure to chickenpox does
not cause shingles. Only a let down in our immune system can
cause shingles.
But shingles can cause chickenpox in people who have not
already had it. So people with shingles need to avoid
contact with those who have not had chickenpox. Just like
chickenpox, shingles blisters are contagious (shedding
active VZV) until the blisters are crusted over and dry.
Shingles has a wide range of symptoms - some individuals
have a mild, painless rash with only a few blisters, while
others may have a severe rash with tremendous pain and
swelling.
It is not known why some people have more symptomatic cases
than others, but overall immune system function probably
plays a role. Also, if the VZV happens to choose a nerve
root that corresponds to a particularly vulnerable area,
such as the eye or the mouth, the symptoms may be more
serious.
Like chickenpox, shingles is very rarely fatal, unless
complications develop. And it is also self-limited, which
means that it will resolve on its own without treatment.
However, unlike chickenpox, shingles may have a serious
aftereffect, called post-herpetic neuralgia. This is
characterized by severe pain along the dermatome that was
affected by the shingles due to nerve damage from the virus.
It usually only lasts days to weeks after the shingles, but
many cases lasting years have been described, and it can
lead to serious disability. That is why shingles, unlike
chickenpox, should be treated with antiviral medication. The
medication doesn’t have much effect on the active shingles,
but if started within 48 hours of a shingles outbreak, it
reduces the chance of developing post-herpetic neuralgia (PHN).
There are a number of safe, effective antivirals on the
market to treat shingles. Even if you have no symptoms from
the shingles themselves, you may be at risk for PHN and
should consider antiviral therapy. An episode of shingles
should always be reported to your doctor.
Other than antiviral treatment to prevent PHN, shingles
should be treated symptomatically with pain relievers and
skin care. Keep the area clean and dry and avoid creams or
lotions that may irritate. If needed, a mild lotion, such as
calamine, can be applied for itching and redness. Just as
your mother always said, do not pick or scratch the
blisters, as they can get infected and cause scars. Shingles
usually take about a week to crust over - unlike chickenpox,
where you continue to develop new blisters during the course
of the illness, all the blisters from shingles erupt at
once.
Although chickenpox and shingles are considered fairly
benign illnesses, there are complications that can occur,
such as infection and PHN. That is why children and adults
who haven’t had chickenpox are advised to get a VZV vaccine.
Hopefully, we’ll see less and less of these illnesses as
more people get protected from them via the vaccine. |
|
