Chickenpox (Varicella)

What does chickenpox look like?

• Chickenpox is caused by the varicella-zoster virus, which also causes shingles.
• Chickenpox is highly contagious and spreads by closeness and contact with someone with chickenpox.
• Fever, malaise, and a very itchy rash (red spots, fluid-filled tiny blisters, and crusted lesions) are all symptoms and signs of chickenpox.
• Treatment for chickenpox is basically supportive.
• Although usually self-limited, chickenpox can also cause more serious complications, including pneumonia, encephalitis, and secondary skin infections.
• The chickenpox vaccine has resulted in a decrease in chickenpox incidence by 90% in the United States.

Chickenpox is a viral infection caused by the varicella-zoster virus (VZV), which is in the herpesvirus family. These viruses infect many tissues during primary infection and then become dormant; they can reactivate later to cause disease. In the case of VZV, reactivation disease is called shingles or herpes zoster and typically occurs when there is a weakened immune system. Before chickenpox vaccine became routine in the U.S., chickenpox was a common childhood disease. Today, it still occurs in populations that are not routinely vaccinated. Varicella-zoster virus is often categorized with the other common so-called "viral exanthems" (viral rashes) such as measles (rubeola), German measles (rubella), fifth disease (parvovirus B19), mumps virus, and roseola (human herpesvirus 6), but these viruses are unrelated except for their tendency to cause rashes. In unimmunized populations, most people contract chickenpox by age 15, the majority between ages 5 and 9, but all ages can contract it. Chickenpox is usually more severe in adults and very young infants than children. Winter and spring are the most common times of the year for chickenpox to occur.

The risk factors for chickenpox are

1. not having immunity against chickenpox by infection or vaccination and
2. exposure to a person with chickenpox or shingles.

Varicella lesions in varying stages of development; SOURCE: CDC

Chickenpox is very highly contagious. It is easily passed between non-immune family members and school classmates through airborne particles, droplets in exhaled air, and fluid from the blisters or sores. It also can be transmitted indirectly by direct contact with articles of clothing and other items exposed to fresh fluid from open sores.

The infected person is contagious up to five days (most often, one to two days) before and five days after the rash appears. It is important for the infected person to stay home away from others while blisters and moist sores are present. When all of the sores have crusted over and are dry, which usually takes about a week, the person is considered no longer contagious.

Because it is so contagious, a non-immune (not vaccinated) person who is exposed to chickenpox is advised to stay home and away from infants and small children or other non-immune people for 21 days after exposure. This is the incubation period before illness occurs. If the person does not become ill in 21 days, he/she may return to usual activities around others. This is very disruptive to school or work. It is not necessary for people who have been vaccinated.

Screening and vaccination for chickenpox is strongly recommended for those who will be working in the health care professions.

When a person with chickenpox must be hospitalized, he/she will be placed in a specially equipped room that vents air harmlessly to the outside environment (negative pressure room). Health care workers will wear gowns and gloves whenever in contact with the patient. These precautions are necessary to prevent non-immune staff and other patients from becoming infected by contact or by airborne virus escaping into the hallway or air handling system.

Varicella virus remains dormant or latent after the acute chickenpox syndrome. It may sometimes be recurrent as a limited area of blisters that look like chickenpox; this syndrome is called shingles or herpes zoster. Shingles is much less contagious than chickenpox. It is not transmitted by airborne virus but rather by direct contact with blisters.

Chickenpox is more complicated at older ages but is usually mild in childhood. It also provides lifelong immunity. Parents have sometimes brought well children to the home of a child with chickenpox for a "chickenpox party" as a way for them to acquire lifelong protection early. This practice may make sense in very resource-poor areas of the world, but it carries the risk of complications of varicella and the long-term risk of shingles later on (which is very painful and has other potential serious complications). Where safe and effective varicella vaccine (chickenpox vaccine) is available it does not make sense to promote immunity this way.

The incubation period (the time from infection to symptoms) is about 14 to 21 days after contact with the virus. Chickenpox is characterized by general weakness, fever up to 102 F, and red spots that start on the same day or so as the fever. The spots rapidly develop into blister-like skin lesions with surrounding redness. Rash usually starts on the head or trunk (the area where most of the rash appears) and spreads to the arms and legs. The blisters may spread to mucous membranes and produce ulcers inside the eyelids, mouth, throat, and genital area. Any area of skin that is irritated (by diaper rash, poison ivy, eczema, sunburn, etc.) is likely to be hard hit by the rash. The rash is typically very itchy (pruritic) and develops in groups of new blisters even as older blisters begin to dry up. Over five to seven days, all of the blisters dry up and become crusted, and the illness is over.

The chickenpox rash is very typical, and diagnosis is usually made based on symptoms and appearance of the rash without having to do any tests. However, people with immune system problems may have an atypical case. In situations where the rash is unclear, fluid or tissue biopsy from a blister or sore can be tested for VZV DNA by PCR.

Picture of varicella (chickenpox) lesions in varying stages of development; SOURCE: CDC

The rash of chickenpox develops in groups with raised red spots arriving first, progressing to blisters filled with clear fluid, like a drop of water on red skin. The blisters may be dimpled in the center. They may break and reform, then finally form sores before drying up as scabs or crusts. They have been described best as grouped blisters on a red base in varying stages of development; some areas may just be forming blisters, while another area may already be crusting over. The crusts will come off on their own, usually without permanent scarring. Scars may occur if sores are scratched or deep, or if bacterial infection occurs, so scratching should be minimized.

Primary care providers usually manage most cases of chickenpox. This includes pediatricians, internal medicine doctors, family medicine doctors, nurse practitioners, and sometimes emergency medicine doctors. Dermatologists or infectious disease specialists may become involved as consultants in complicated cases or cases at high risk for severe disease, such as pregnancy, adults, eczema, or immune deficiency.

Most of the treatments for chickenpox are aimed at decreasing the symptoms, such as severe itching. A non-aspirin analgesic like acetaminophen (Tylenol) can be used to decrease the fevers and aches. Children should never be given acetylsalicylic acid (aspirin) or aspirin-containing cold medications because of the risks for developing Reye's syndrome (a severe brain disease associated with liver and brain dysfunction and death).

Frequent oatmeal baths (plain oatmeal in water, Aveeno, etc.) can decrease the itching associated with chickenpox. In addition, soothing lotions and moisturizers such as calamine lotion or any other similar over-the-counter preparation can be applied to the rash. Diphenhydramine (Benadryl) or other antihistamines can be helpful in controlling the itching. Always discuss these treatment options with your health care practitioner.

In addition to medications, there are also preventive measures that are needed. For young children, it is important to keep nails trimmed in order to minimize injury due to scratching and to control the risks for secondary bacterial infections like impetigo or Staphylococcus (staph infection).

Lastly, in severe cases or people at high risk for severe disease, acyclovir (Zovirax) can be prescribed. Acyclovir is an antiviral drug that has been used to shorten the duration of the infection. This medication has only been shown to be effective if started within one to two days of onset of the chickenpox rash. Most commonly, this treatment is reserved for patients with other diagnoses that put them at risk for severe disease (adults, pregnant women, severe skin diseases, immunodeficiency).

Chickenpox is usually treated at home with over-the-counter medications for fever, antihistamines for itching, soothing oatmeal baths, and calamine lotion.

Complications can and do occur from chickenpox and may fatal. Infection of the open pox sore by bacteria can injure the skin, sometimes causing scarring, especially if the patient scratches the inflamed area. Bacterial skin infection with group A Streptococcus ("strep" or "impetigo") is, in fact, the most common complication of chickenpox in children. Other complications are much less common. In children, the central nervous system may be affected. A disorder of the cerebellar portion of the brain ("cerebellitis" or "cerebellar ataxia") may occur with wobbliness, dizziness, tremor, and altered speech. Encephalitis (inflammation of the brain with headaches, seizures, and decreased consciousness) may occur as well as damaged nerves (nerve palsies). Reye's syndrome, a potentially fatal combination of liver and brain disease, may occur in children who take aspirin or salicylate products. (Children with fever should not take aspirin.) Other complications include bloodstream infection (sepsis or "blood poisoning" from skin infection) and dehydration. Death from varicella may occur even in healthy children.

Pneumonia is the most common complication in teens through adults and can be life-threatening. Most adults who have died of varicella were infected by unvaccinated children.

After primary infection has resolved, usually later in life or during a period of weakened immunity, VZV may cause herpes zoster or shingles, which can have a number of complications. People with certain conditions are at higher risk of severe complications and death:

• Human immunodeficiency virus (HIV or AIDS)
• Lupus and other connective tissue or autoimmune diseases
• Leukemia and other cancers
• People taking immune-suppressing drugs, such as cortisone-related medications, tumor necrosis factor inhibitors, and chemotherapy
• People who have had transplants
• Pregnancy
• Infants, teens, and adults

A pregnant woman who has never had chickenpox or the vaccine should avoid touching or being in the same room as a person with suspected chickenpox. Not only is she at risk for pneumonia caused by the chickenpox virus, the fetus is at risk for infection in the womb (congenital varicella syndrome) up until 20 weeks gestation. Congenital varicella causes multiple birth defects, such as skin scarring and malformed limbs. It is fortunately very, very rare. Newborn infants whose mothers develop chickenpox five days before or two days after birth are at highest risk of severe chickenpox. These babies may develop symptoms within two weeks of birth. This is because there is not enough time for the mother to develop varicella antibody to pass on to the baby. The fatality rate for these babies is up to 30%. If the baby develops symptoms at 10-28 days of age, it is likely to be mild.

Latent VZV can reactivate from a cutaneous nerve to cause a chickenpox-like rash, but instead of being widespread, the rash is limited to the area of skin involving one or two nerve roots and may last up to four weeks. This is called herpes zoster or shingles, which may cause itching or even severe, burning pain. This pain is called postherpetic neuralgia (PHN) and may last for weeks to months.

PHN occurs in about 10% of individuals over 40 or immunocompromised patients. This nerve problem may be disabling, and it does not respond to over-the-counter medications or even narcotics. It often must be treated with anti-seizure medications to reduce pain. This medications can have their own important side effects and limit daily activities. In addition, shingles may be treated with antiviral and corticosteroid drugs, which may also have significant side effects.

Shingles can break out in any area of the body depending on which nerve roots are involved. It is impossible to predict where it will break out.

One important complication of shingles is blindness if the outbreak occurs in the nerves to the eye (ocular nerves). Another complication occurs with involvement of the auditory nerves, called Ramsay Hunt syndrome. This syndrome may cause severe ear pain, hearing loss, severe dizziness or vertigo, and nausea that is difficult to treat. This may last for several weeks and be disabling.

In some cases of severe immune deficiency, such as after chemotherapy, shingles may become widespread (disseminated). Essentially, it becomes widespread similar to primary chickenpox infection. Disseminated shingles is as contagious as chickenpox and can be transmitted by airborne droplets, as well as contact with blister fluid.

Shingles has been associated with inflammation of blood vessels (vasculitis) and may be associated with an increased risk of strokes in the months after the outbreak. VZV has been detected in blood vessels of people affected by giant cell arteritis (temporal arteritis), which is associated with sudden, permanent blindness and other problems.

Shingles is contagious to nonimmune people who have direct contact with fluid from the blisters or open sores. The only situation in which shingles can be transmitted by airborne droplets is when it is disseminated, like primary varicella or chickenpox.

In health care settings, people with shingles are placed on contact precautions, which means people must wear protective gowns and gloves whenever in contact with the patient.

Disseminated shingles requires the same airborne precautions as chickenpox, in addition to contact precautions. The patient must be placed in a room that is specially equipped to vent infectious air harmlessly to the outside. This is called negative pressure ventilation. It is used whenever there is a risk of airborne infectious particles escaping into the hospital hallway or air handling system.

If this happens, the exposed individual should be offered varicella-zoster immune globulin (VZIG or VariZig). VZIG provides about two weeks of protective antibody, which is enough time for the antibodies to neutralize the virus and reduce infection.

Individuals who should receive post-exposure VZIG include nonimmune pregnant women, immunocompromised individuals, newborns whose mothers had chickenpox five days before to two days after birth, and premature infants. VZIG is given as one dose as soon as possible after exposure to VZV and up to 10 days afterward, or at any time during hospitalization in the case of hospitalized premature infants.

Yes, it is highly effective and recommended by the American Academy of Pediatrics (AAP) and Advisory Committee on Immunization Practices (ACIP). Varicella vaccine has reduced the numbers of chickenpox cases and their complications by 90%. The current aim in the U.S. and many other countries is to achieve universal (or nearly universal) immunization of children with the chickenpox vaccine (varicella vaccine). The vaccination requires only two shots, may be combined with MMR (MMRV) in one vaccine, and is very safe and effective. The first vaccination is given at 12 to 15 months of age, and the second (booster) is given at 4 to 6 years of age. Catch-up vaccination in those who missed it in early childhood can be given at any time until adulthood, as long as a total of two doses have been given at least one to two months apart.

If an older person has not had chickenpox, the vaccine may be given at any time, although those over 50 should receive the shingles vaccine. There have been very few vaccine side effects. All but those with a compromised immune system should have the vaccination.

Unfortunately, varicella vaccine is the most commonly refused childhood vaccine; parents may still view chickenpox as the least severe vaccine-preventable disease. Prior to varicella vaccine licensure in 1995, however, there were 4 million cases of chickenpox infection annually, resulting in more than 10,000 hospitalizations and 100 deaths per year in the United States. Since licensure, universal immunization has reduced by 80% the annual morbidity, mortality, and hospitalizations from chickenpox.

The difference between these vaccines may be confusing, so they are conventionally referred to as chickenpox vaccine and shingles vaccine, to better distinguish them.

Varicella vaccine (also called chickenpox vaccine) is a live varicella virus strain that is formulated for nonimmune individuals. It does not cause widespread infection like wild-type varicella virus but only local infection, enough to stimulate new, protective levels of antibodies. It is typically given in children or adolescents, but adults may receive it. The current FDA-approved varicella vaccine is called Varivax. It may also be formulated with measles, mumps, and rubella (MMR) vaccine as MMRV, or ProQuad.

Childhood vaccination with Varivax or ProQuad is given at age 12-15 months of age and 4 to 6 years of age. Varicella vaccine sometimes causes local blisters within two weeks in the injection area. Because the dose of virus is higher in Varivax, there is a small risk of transmission to others, and contact with immune suppressed people and nonimmune pregnant women should be avoided until healed. As live vaccines, ProQuad and Varivax should not be given to those with immune system problems.

Varicella vaccination is important for children, but it should also be considered for nonimmune adults who work with children, women who are planning pregnancy, health care professionals, travelers, correctional institutions, and military personnel. Adults born before 1980, when chickenpox was common, are assumed to have antibodies to it. Adults born after 1980 or outside the U.S. can be screened for VZV antibodies before being offered vaccine. It is given as two doses at least four to eight weeks apart at ages 13 and over. Adults 50 years of age and over will usually receive the shingles vaccine instead.

Varicella-zoster vaccine (shingles vaccine) is formulated to boost varicella antibodies in older adults. The shingles vaccines are indicated for adults over 50 years of age; most adults currently in this age group have had chickenpox, whether they recall it or not. There are two brands of FDA-approved shingles vaccines: Zostavax and Shingrix. Zostavax is a live varicella virus vaccine that is FDA-approved to be given in one dose after age 50, however, there was no data on duration of protection, and the risk of complications from shingles is highest in those over 60 years of age. For this reason, the ACIP recommended administering Zostavax to those aged 60 and above; this decision was supported by later data showing a significant drop in protection 10 years after vaccination. Zostavax is a live vaccine, and some may develop blisters at the site of injection or very rarely disseminated lesions. Due to the theoretical risk of transmission, lesions should be covered, and contact with immunosuppressed or nonimmune pregnant individuals should be avoided until healed.

While boosters of Zostavax were being debated, the newer Shingrix vaccine was developed, and is now preferred. Shingrix is a non-live antigen (a VZV protein that stimulates antibodies) with an adjuvant (a molecule that activates the immune system). It is given as two doses at least eight weeks apart. Data has shown that protective levels of antibodies from Shingrix last much longer than that produced by Zostavax. As of January 2018, the ACIP has recommended Shingrix as the preferred vaccine for the prevention of shingles and its complications in older adults, starting at the FDA-approved age of 50.

An anticipated advantage of a non-live vaccine, Shingrix may have potential use in immunocompromised individuals who are at risk for more serious complications of shingles, such as dissemination. The ACIP awaits further evidence before recommending it as safe and effective in these individuals.

The prognosis of uncomplicated chickenpox is generally good when acquired in childhood, and even in most adults, after the chickenpox rash goes away. Most people never experience chickenpox symptoms again after the first occurrence, and they are immune to other people's chickenpox. This is because the virus remains dormant in the nervous system; this also means that chickenpox can sometimes resurface later in life as shingles (zoster).

The prognosis of shingles is generally best in younger individuals, although it still causes significant discomfort. The prognosis is poorer the older the individual is when shingles occurs. This is why shingles vaccination is so important for people over the age of 50.