The Shingles-Chicken Pox Connection

One Virus Causes Both

          Several recent questions from our readers made me realize that confusion abounds when it comes to shingles and chicken pox and the connection between the two.  Chicken pox (varicella) was once a right of passage for every child born before the varicella vaccine became available in the United States in 1995.  It is so highly infectious that very few escaped into adulthood without contracting chicken pox, which then conferred immunity to the virus that causes it.  In fact, more than 90% of adults test positive for immunity to varicella from exposure in childhood.  It is now recommended that children receive the varicella vaccine, which contains live attenuated virus, in two doses, the first between 12 and 15 months and the second between 4 and 6 years of age.  Children who receive the vaccination for chicken pox will either avoid contracting the infection or have a milder case of shorter duration.  Even more importantly they can avoid the rare but serious complications that sometimes occur. 

          For those who have had either chicken pox or the varicella vaccine to prevent it, the virus lies dormant in the sensory nerve ganglia near the spine where it is kept under control by the immune system.  The latent virus can reassert itself at a later time, often many years later, in the form of a painful rash known as shingles (herpes-zoster), if the immune system loses its ability to keep it under control.  It is important to understand, then, that both chicken pox (varicella) and shingles (herpes zoster) are caused by the same human herpesvirus known as varicella-zoster. 

Chicken Pox 

          In unimmunized populations, chicken pox is most common in children under the age of 12.  It is an acute illness with a characteristic itchy rash often accompanied by flu-like symptoms, including fever, headache and abdominal pain.  The rash occurs 10 to 20 days after exposure and begins on the face, scalp and trunk first, then spreading out to the extremities.  The rash begins as crops of pimples that become fluid filled vesicles which crust over within about a week.  Patients with chicken pox are contagious one to two days before the rash appears and until all the lesions have crusted over.  It is spread by respiratory secretions or direct contact with fluid from the vesicles. 

          Serious complications include bacterial skin infections from scratching the lesions, encephalitis, cerebellar ataxia and pneumonia.  Newborns, older children and adults, as well as those with compromised immune systems, are at greatest risk of complications.  If a women who has not had chicken pox or the varicella vaccine contracts chicken pox during pregnancy, her child could be at risk of having birth defects.  Anyone who has not had chicken pox or the varicella vaccine can catch chicken pox from someone with an active case of shingles, but cannot contract shingles itself.  Shingles can only occur from a reactivation of the varicella-zoster virus in someone who has previously had chicken pox or the varicella vaccine. 

Shingles 

          Shingles or herpes zoster occurs when immunity wanes due to aging, stress, or diseases such as malignancy or as a result of therapy that suppresses the immune system.  It is more likely to occur after the age of 50 and approximately 30% of people will develop shingles sometime during their lifetime and usually only once.  Shingles only occurs in those who have had either chicken pox or the varicella vaccine.  When the chicken pox virus is reactivated in the sensory nerve ganglia it results in a painful, burning rash in the distribution of that nerve.  The rash is therefore located on only one side of the body often appearing as a narrow band or strip extending from the spine around to the front.  While the rash is most often in the trunk area, other areas can be involved. 

          When the latent virus is reactivated in the trigeminal nerve supplying the face, severe involvement of the eye can occur, sometimes leading to blindness.  Often before the rash appears the patient will experience intense itching and pain in that area.  The lesions begin as a red rash progressing to blisters which usually crust over within a week to 10 days.  Patients with shingles can also experience malaise, fever, chills and headache.  One of the most unpleasant complications of shingles is known as post-herpetic neuralgia, a condition where the pain persists after the rash has resolved. 

Prevention and Treatment 

          Chicken pox:  Even after completing the two recommended doses of the varicella vaccine, it is still possible to get chickenpox.  The disease in such cases is usually milder.  Older children between 7 and 12 years of age who have not received the vaccine should receive two catch up doses at least three months apart.  It is also recommended that individuals 13 years and older who have never had chicken pox or the varicella vaccine receive two doses of the vaccine at least 28 days apart.  For children who develop chickenpox, keeping the fingernails trimmed may help prevent bacterial skin infection caused by scratching the itchy lesions.  Oral antihistamines may also help the itching.  Antiviral medications, such as acyclovir, may be used in patients with eczema, asthma or immunosuppression, but are only helpful if started within 24 hours of the development of the rash.  Tylenol (acetaminophen) may be used for fever and pain, but aspirin should never be used in children because of the possibility of Reye’s syndrome.  Because the infection is so contagious, children with chicken pox should be kept out of school until all the lesions have crusted over, usually about ten days from onset of symptoms. 

          Shingles:  Shingles can also be treated with antiviral medications if started within 24 hours of the onset of symptoms.  Several other medications are available to specifically help control the pain of post-herpetic neuralgia.  The zoster vaccine has been recommended for individuals older than 60 years by the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) recently approved the use of the vaccine in individuals 50 and older.  Studies have shown that the incidence of shingles is about 50% lower in individuals who have been vaccinated and the incidence of post-herpetic neuralgia is about 67% lower.  Your personal physician should be able to answer any questions you have about chickenpox, shingles or the vaccines used to prevent either illness.