Chicken pox, also called varicella, is an infection caused by the varicella zoster virus. It's usually thought of as a childhood disease since children account for about 90 percent of chicken pox cases. However, chicken pox may also occur in teens, adolescents and adults and is characterized by the appearance of a rash consisting of itchy, blistery bumps that spread across the body over the course of the infection.
It's thought that chicken pox may have originated in Africa before spreading to other areas of the world. So named because it makes the skin look like that of a plucked chicken, the virus was often confused with smallpox until the 1900s. In the 1600s, English physician Richard Morton assumed that the two were the same disease and that chicken pox was simply a milder form. It wasn't until 1767 that another English doctor, William Heberden, discovered that each was a separate disease with distinct pathology.
Though the first official description of chicken pox appeared in the 1500s and is attributed to Giovanni Filippo, it wasn't until 1875 that the condition was discovered to be caused by an infectious agent. In 1972, nearly 100 years later, Takahashi isolated the virus and developed the first chicken pox vaccine. The serum was approved for use in Japan and Korea in 1988 before being adopted in the US in 1995.
People all over the world get chicken pox, though climate affects the distribution of the virus among age groups. In temperate places, preschool and school-aged children are most likely to contract the disease during the late winter and early spring seasons. Older children and adolescents are more at risk for chicken pox infection if they live in tropical zone. Adults in these areas also have a higher susceptibility to the disease.
Many countries vaccinate healthy children against chicken pox, and doing has been shown to help reduce cases by marked amounts. Before the US started its vaccination program in 1995, over four million people contracted chicken pox annually. According to the Centers for Disease Control and Prevention (CDC), 10,600 of those four million were hospitalized and 100 to 150 died from the disease. Thanks to vaccination, most people in the US no longer contract chicken pox or only come down with a mild form of the virus.
Individuals who travel to countries where chicken pox vaccines aren't administered may be at risk for developing an infection. The risk is greater for travelers who have never had chicken pox or never received a vaccine during their lifetimes.
Risk Factors and Development
Whether they're exposed at home or abroad, the groups at highest risk for contracting chicken pox include:
- People who have never had the virus
- Unvaccinated individuals of all ages
- Anyone who works around children such as school and daycare employees
- Family members in households with young children
After initial exposure, the varicella virus goes through an incubation period of ten to 21 days. This means it can take anywhere from two to three weeks for the telltale bumps to appear. The virus usually enters the body via the respiratory tract or the eyes and begins to replicate in the upper area of the throat, known as the nasopharynx, as well as in the lymph nodes. It then spreads to other organs before manifesting as a telltale skin rash.
The most common symptom of chicken pox is a rash of red bumps that develop into itchy blisters, but it is often preceded by other symptoms, particularly in older individuals. In children, the rash may be the first thing to appear. However, children can also present with:
- Runny nose
- Stomach ache or general nausea
Adults may have similar symptoms or develop a fever higher than that of what children experience. Muscle aches may also be present. Whether or not these specific symptoms appear, most people who come down with the chicken pox report a general feeling of being unwell for a couple of days prior to developing a rash.
When the rash appears, it often starts somewhere on the torso. From there, it commonly spreads to the face and limbs, though blisters can form anywhere including behind the ears, under the arms and even in the mouth. Most people develop between 250 and 500 blisters over the course of the infection.
Chicken pox blisters form in clusters that start out as small red bumps but quickly progress to blisters filled with a yellowish fluid. In a day or two, the fluid turns cloudy and eventually leaks out of the blister. The bumps then develop a scab or crust over the top and begin to heal up. This process may occur in several waves and results in spots at various stages of development and healing. Scabbed blisters should fade on their own as the infection begins to clear.
Once the initial rash progresses from spots to blisters, it becomes very itchy. This can cause a great deal of discomfort for both children and adults and may require at-home or over-the-counter treatment to ease the pain. Although the infectious stage of the disease only lasts for a couple of weeks, the rash may linger for as long as a month before healing completely.
Doctors can often diagnose chicken pox just by looking at a patient and asking a few simple questions. The rash and blisters are easy to recognize but may occasionally be mistaken for another type of skin condition during the early stages. If there's any question or uncertainty, a blood test or a culture of liquid from the blisters can be used to confirm a chicken pox diagnosis.
Patients should expect their doctors to ask questions about symptomology leading up to the appearance of the rash as well as whether or not they're aware of having been exposed to an infected individual. Doctors will also ask about recent and current medications to determine whether or not a patient's immune system may be compromised. Parents bringing their children in for a diagnosis should have a list of medications, allergies, symptoms and other important information on hand to share with the doctor.
If the virus is present, blood tests will show elevated IgM antibodies, which indicate an acute infection. IgG antibodies show immunity to the disease. The preferred method for diagnosis, however, is a polymerase chain reaction (PCR) test in which doctors look for the DNA of the virus in samples from an infected person.
Pregnant women who contract chicken pox and are concerned about the infection spreading to the baby can get an ultrasound about five weeks after maternal symptoms develop. It's also possible to perform DNA testing on the amniotic fluid, but this method carries high risks for the unborn child and may be more dangerous than the virus itself.
It's a good idea to have other family members checked for chicken pox if one person in the household contracts the virus. In some cases, people living with an infected individual may develop a more severe form of the disease following exposure.
Due to the highly contagious nature of chicken pox, children and adults with the virus should avoid contact with other people until the infection has cleared. That means staying home until all blisters have crusted over or a doctor gives the all clear. Returning to school or work too early puts others at risk of catching the virus, especially those who haven't been vaccinated.
Treating chicken pox is similar to treating the flu. Infected individuals need plenty of rest and nourishing fluids, especially water, during recovery. Healthy food is also a must to give the body what it needs to fight off the infection and heal completely.
Over the counter medications such as acetaminophen and ibuprofen can be used to manage the pain and fever associated with chicken pox. However, parents shouldn't give painkillers to children without first checking with a doctor, and children should never be given aspirin. Administering aspirin at a young age may cause a potentially serious complication known as Reye's syndrome. Pregnant women should also check with their doctors before taking any kind of pain medication.
Doctors may be able to administer an antiviral medication that eases the severity of chicken pox symptoms if the infection is diagnosed within one day of the emergence of the rash. Medication isn't usually given to otherwise healthy children but may help those at risk for complications such as older children and adults. People with preexisting skin conditions, lung problems or who have recently taken drugs such as steroids which suppress the immunity may also be candidates for antiviral treatment.
For many people, the itchiness associated with chicken pox is the worst part of the infection. Since scratching blisters increases the risk of transmitting the disease and may lead to other infections, it's important to manage this symptom in every way possible. Fingernails should be kept trimmed to minimize damage from scratching, and it may be necessary to put mittens or socks over children's hands at bedtime to keep them from accidentally itching in their sleep.
Calamine lotion or cooling gels can be used to soothe inflamed skin and reduce the urge to scratch. Taking a cool bath with additives such as baking soda, oatmeal or cornstarch has also been shown to have a soothing effect. Antihistamines may be administered should the itchiness become severe, but parents should consult a doctor before treating their children with these medications.
To minimize skin irritation, people with chicken pox should wear light clothing made from nonabrasive fabrics such as cotton. Bedding should also be light and soft, especially for children. If baths are used as a treatment method, it's important pat skin dry using the softest towel possible rather than rubbing it. Heat and humidity can make itchiness worse, so infected individuals should try to remain in a comfortable, dry environment during the course of the infection.
Cold foods can be soothing in cases where blisters appear in the mouth. Hot and spicy dishes shouldn't be eaten until after the infection has cleared. Soft foods are easier to handle and won't scrape or irritate blisters before they scab over. Good choices include foods such as popsicles, applesauce and bananas as well as cooled cereals such as oatmeal or farina.
In general, chicken pox is only contracted once during a person's lifetime and results in permanent immunity from future infections. With symptom management and proper rest, the virus should clear on its own and not appear again.
In most cases, the varicella virus runs its course without a problem. However, there are some instances in which serious side effects or complications may develop. Risk for complications from chicken pox is higher in:
- Teens and adolescents over 15 years of age
- Infants less than 1 year old
- Children of mothers who never contracted the virus or were never vaccinated
- Unvaccinated pregnant women
- Immunocompromised individuals
- People who are taking or have recently taken immunosuppressant drugs
Mortality rates from chicken pox complications are low, with about one in 40,000 individuals dying as a result of the disease or associated conditions.
It's generally recognized that chicken pox is more dangerous for adults than children. Adults who contract the varicella virus are more likely to experience difficulties during the natural course of the disease. One common problem is infection of the skin around blisters. The skin surface may become painful and red and a green discharge may form. Any of these symptoms should be evaluated by a doctor to determine if an antibiotic is necessary to clear up the infection.
Varicella pneumonia, a rare complication that occurs when the chicken pox virus spreads to the lungs, may develop two to 10 days after the first appearance of a varicella rash. Initial symptoms include fever and cough, and the infection may persist for anywhere from a few weeks to a few months. People who smoke and those with chronic lung disease are at higher risk for varicella pneumonia.
Certain symptoms such as stiff neck, sleepiness and lethargy shouldn't be ignored as these may be signs of a serious condition such as meningitis or encephalitis. These infections, which involve inflammation of the spinal cord and brain, can cause serious problems or death if left untreated. Some adults with chicken pox develop myocarditis, a condition involving inflammation of the heart muscle. This occurs if the initial virus travels to the heart and causes a secondary infection. In serious cases, myocarditis can lead to heart failure.
A chicken pox infection may also put adults at risk for:
- Toxic shock syndrome
- Bone or joint infections
- Bleeding disorders
- Soft tissue bacterial infections
One common complication from chicken pox may not show up until years after the initial infection. Shingles, called zoster and caused by the same virus, appears in one in 10 adults and causes a painful rash. The name "zoster" comes from the Greek word for "girdle" and refers to the fact that, unlike with chicken pox, shingles blisters commonly appear only around the right or left side of the torso. This reactivation of the varicella virus may be caused by stress, weakened immunity or certain medications.
In addition to a rash, shingles may manifest with headaches or flulike symptoms unaccompanied by fever. More severe symptoms include dizziness, weakness, facial pain or vision changes, all of which should be checked by a doctor. Shingles rashes that spread to other parts of the body may also be cause for concern. In most cases, shingles clears up in two to four weeks. Although shingles can't be passed from person to person, it is possible for an individual with shingles to pass a varicella infection to someone who has never had chicken pox.
In 2006, the US approved a vaccine to protect against shingles in individuals 60 years of age and older. Since shingles may cause serious complications such as nerve or neurological damage, older adults who had chicken pox in the past should consider getting inoculated.
Most childhood cases of chicken pox are straightforward and clear up without any associated problems. However, it's possible for children to develop complications similar to those experienced by adults such as skin infections, meningitis or encephalitis. Skin problems are the most common with as many as one in 20 kids contacting a bacterial skin infection during the course of the disease.
Children may also develop a condition known as cerebellar ataxia, which manifests as an unsteady walk or other difficulties with movement. Seen mostly in children under three years of age, this condition isn't usually a concern if it appears as the result of a viral infection and should go away on its own.
More severe complications of childhood chicken pox infections may include Reye's syndrome, a condition that results in swelling of both the brain and the liver. Symptoms of this potentially serious condition include vomiting, convulsions and drowsiness and may appear in children or teenagers who are recovering from the varicella virus. The condition has also been associated with aspirin, which is why the medical community advises against administering the painkiller to young people.
Risk of arterial ischemic stroke (AIS) appears to be higher in children who have had chicken pox than those who haven't. Some studies show a significant correlation between previous infection and stroke. As many as 31 percent of kids may experience AIS within a year of a chicken pox infection. This could be due to vascular damage in the brain as the result of the varicella virus.
In Pregnant Women and Babies
Women without inherent immunity from vaccination or a previous chicken pox infection are at higher risk for complications should they come down with the virus while pregnant. Varicella poses a danger to both mother and child. The highest risk to the unborn baby occurs if the infection is contracted within the first six months of pregnancy. Infection in the last three months poses more of a danger to the mother.
Although pregnant women aren't eligible for the chicken pox vaccine, they may be able to receive a varicella-zoster immune globulin shot to reduce the severity of the infection if they become exposed. This may help lessen the risk of complications such as varicella pneumonia, which is more common in pregnant women than other adults.
Contracting chicken pox early in pregnancy may lead to fetal varicella syndrome in the unborn child if the infection spreads through the placenta within the first 28 weeks of development. Also called congenital varicella syndrome, this serious disease can cause many problems with growth, including:
- Damage to the optic stalk and cup as well as the lenses of the eyes
- Optic atrophy
- Encephalitis or other brain damage
- Damage to the spinal cord
- Problems with movement and senses
- Deficient or absent deep tendon reflexes
- Poor development of limbs and/or extremities
- Malformation of the anal and/or bladder sphincter
Infected mothers are also more likely to experience premature delivery. In some rare cases, pregnant women who contract chicken pox close to the time of delivery can pass the infection on to the infant, a condition known as neonatal varicella. If the infection appears anywhere from five days before to two days after birth, infants don't receive antibodies from their mothers and may be 30 percent more likely to die from varicella complications than those who inherit immunity.
Symptoms of neonatal varicella generally appear at the age of ten to 12 days and come with an increased risk of developing pneumonia. To help stave off these effects, infants may be inoculated with varicella-zoster immune globulin soon after birth or treated in an isolation room at the hospital until the infection clears.
Although most people will get chicken pox once in their lifetimes, it's possible to avoid infection by taking cautionary preventative measures.
Chicken pox can spread through the air as well as by direct contact with an infected individual. The virus can easily spread for the first week of infection and is contagious from about two days before the rash appears until the blisters scab over four to five days later. Transmission before the development of a rash is usually via fluids from sneezing, coughing or a runny nose.
About 90 percent of people who haven't had chicken pox will come down with it if exposed, so it's important to stay away from others who have it during this period. Anyone with a weakened or compromised immune system must exercise extra caution.
Like other viruses, varicella zoster is transmitted via bodily fluids. Sneezing, coughing, and scratching fluid-filled blisters are all common ways that chicken pox can spread. It's also possible to catch chicken pox from someone who has shingles since both infections are caused by the same virus. However, shingles can't be contracted from a person with chicken pox, nor is it possible to come down with chicken pox as the result of indirect contact.
Once chicken pox blisters have crusted over, the infection is no longer contagious. Since blisters can appear in cycles, it's important to monitor the rash for any fresh outbreaks before resuming normal activities.
Since contact with bodily fluids from an infected individual is the primary way that chicken pox spreads, cleanliness is extremely important. Bedding, clothing and towels used by children or adults with the disease should be changed and washed frequently to remove these fluids.
People of all ages can get the chicken pox vaccine in the US, though the vaccine is generally administered to children at a young age to prevent future infections. The first dose is given when at 12 to 15 months old with a second dose following between the ages of 4 and 6. Children ages 7 to 12 may receive two doses three months apart while those over age 13 need a space of at least four weeks in between. Unvaccinated adults should space doses out over a span of four to eight weeks. It's especially important for women who want to get pregnant and have never had chicken pox to consider vaccination to avoid potential complications.
Individuals may be ineligible for the vaccine if they are:
- Allergic to gelatin
- Allergic to neomycin
The vaccine is considered safe for babies, children, adolescents and adults. Some people may experience minor side effects such as redness, soreness, swelling or bumps near the injection site. In rare cases, a rash similar to chicken pox will develop and form a handful of mild blisters. Vaccination is considered 70 to 90 percent effective in preventing infection and 90 to 100 percent effective in staving off moderate to severe cases of the disease. Breakout infections may still occur in a small number of people who get the vaccine.
Children and adults who receive the chicken pox vaccine may contract a mild form of the disease that manifests with only a few dozen blisters and clears up within a few days. These cases aren't usually accompanied by a fever and carry little risk for complications in healthy individuals.
Children whose mothers have had chicken pox don't always contract the virus because antibodies may be passed on from parent to child. However, due to the potential for complications in adulthood, it's best to opt for the vaccine.
Some people already carry inherent immunity to chicken pox and don't need to be concerned about getting vaccinated or contracting the infection. According to the CDC's Advisory Committee on Immunization Practices (ACIP), a person is considered immune to varicella if:
- They can provide documentation of vaccination at any stage of life
- A previous infection of chicken pox or shingles was diagnosed and documented
- Lab tests show antibodies indicating immunity
- They were born in the US before 1980 and are not currently a health care worker, pregnant or immunocompromised
Every state in the US requires children to be vaccinated against chicken pox before entering school. This includes older children and college-bound adolescents who didn't receive the vaccine in infancy. Individuals of all ages can be tested for proof of inherent immunity to determine whether or not the vaccine must be administered prior to attending school.
Avoid "Chicken Pox Parties"
Before the chicken pox vaccine became available, it was common for parents to throw "chicken pox parties." Set up like a regular party or playdate with toys, games and food, these parties always include at least one child with an active chicken pox infection on the premise that, since kids are going to get chicken pox anyway, it's best to get the ordeal over with sooner rather than later. In some cases, parents even encourage their children to share snacks or drinking glasses to promote the spread of the virus.
Doctors warn against such intentional exposure due to the potential risks associated with chicken pox. Until vaccination became common, anywhere from 100 to 150 children died every year from the virus or problems associated with it. Those in the medical community point out that these risks exist even for otherwise healthy children, and allowing them to contract varicella could result in unintentional infection of others whose immune systems aren't well equipped to fight off the virus.
Parents opposed to vaccination still host these parties with the belief that "natural" infection is safer than artificial inoculation. Some even attempt to obtain infected material such as half-eaten lollipops through the mail and give them to their children. This practice is not only dangerous but also illegal in the US. Unvaccinated children may spread chicken pox to infants, other kids and adults who also haven't had the vaccine or who never contracted the virus when they were younger.
Whatever the reason for holding a chicken pox party, doctors continue to discourage the practice and urge parents to opt for the option of vaccination for their children.
Although chicken pox is a common disease and still appears all over the world, it's smart to take precautions against contracting the virus. Good hygiene, avoidance of infected individuals, vaccination and other measures promote wellness and can help people of all ages avoid an itchy situation.