Chickenpox is caused by the varicella-zoster virus (human herpesvirus type 3); chickenpox is the acute invasive phase of the infection, and herpes zoster Herpes Zoster Herpes zoster is infection that results when varicella-zoster virus reactivates from its latent state in a posterior dorsal root ganglion. Symptoms usually begin with pain along the affected... read more (shingles) represents reactivation of the latent phase.
Chickenpox, which is extremely contagious, is spread by
Mucosal (usually nasopharyngeal) inoculation via infected airborne droplets or aerosolized particles
Direct contact with the virus (eg, via skin lesions)
Chickenpox is most communicable during the prodrome and early stages of the eruption. It is communicable from 48 hours before the first skin lesions appear until the final lesions have crusted. Indirect transmission (by carriers who are immune) does not occur.
Prior to the advent of the varicella vaccine Varicella Vaccine Varicella vaccination provides effective protection against varicella (chickenpox). It is not known how long protection against varicella lasts. But, live-virus vaccines, like the varicella... read more , chickenpox epidemics occurred in winter and early spring in 3- to 4-year cycles.
(See Overview of Herpesvirus Infections Overview of Herpesvirus Infections Eight types of herpesviruses infect humans ( see Table: Herpesviruses That Infect Humans). After initial infection, all herpesviruses remain latent within specific host cells and may subsequently... read more .)
Symptoms and Signs of Chickenpox
In immunocompetent children, chickenpox is rarely severe. In adults and immunocompromised children, infection can often be serious.
Mild headache, moderate fever, and malaise may occur 7 to 21 days after exposure, about 24 to 36 hours before lesions appear. This prodrome is more likely in patients > 10 years and is usually more severe in adults.
The initial rash, a macular eruption, may be accompanied by an evanescent flush. Within a few hours, lesions progress to papules and then characteristic, sometimes pathognomonic teardrop vesicles, often intensely itchy, on red bases. The lesions become pustular and then crust.
Lesions evolve from macules to papules and vesicles, which then crust. A hallmark of chickenpox is that lesions develop in crops so that they are in various stages of development in any affected region. The eruption may be generalized (in severe cases) involving the trunk, extremities, and face, or more limited but almost always involves the upper trunk.
Ulcerated lesions may develop on the mucous membranes, including the oropharynx and upper respiratory tract, palpebral conjunctiva, and rectal and vaginal mucosa.
In the mouth, vesicles rupture immediately, are indistinguishable from those of herpetic gingivostomatitis, and often cause pain during swallowing.
Scalp lesions may result in tender, enlarged suboccipital and posterior cervical lymph nodes.
New lesions usually cease to appear by the 5th day, and the majority are crusted by the 6th day; most crusts disappear < 20 days after onset.
Sometimes vaccinated children develop varicella (called breakthrough varicella); in these cases, the rash is typically milder, fever is less common, and the illness is shorter; the lesions are contagious.
Secondary bacterial infection (typically streptococcal or staphylococcal) of the vesicles may occur, causing cellulitis or rarely necrotizing fasciitis or streptococcal toxic shock.
Pneumonia may complicate severe chickenpox in adults, neonates, and immunocompromised patients of all ages but usually not in immunocompetent young children.
Myocarditis, hepatitis, and hemorrhagic complications may also occur.
Acute postinfectious cerebellar ataxia is one of the most common neurologic complications; it occurs in 1/4000 cases in children.
Transverse myelitis Acute Transverse Myelitis Acute transverse myelitis is acute inflammation of gray and white matter in one or more adjacent spinal cord segments, usually thoracic. Causes include multiple sclerosis, neuromyelitis optica... read more may also occur.
Reye syndrome Reye Syndrome Reye syndrome is a rare form of acute encephalopathy and fatty infiltration of the liver that tends to occur after some acute viral infections, particularly when salicylates are used. Diagnosis... read more , a rare but severe childhood complication, may begin 3 to 8 days after onset of the rash primarily following the use of aspirin.
In adults, encephalitis Encephalitis Encephalitis is inflammation of the parenchyma of the brain, resulting from direct viral invasion or occurring as a postinfectious immunologic complication caused by a hypersensitivity reaction... read more , which can be life threatening, occurs in 1 to 2/1000 cases of chickenpox.
Diagnosis of Chickenpox
Chickenpox is suspected in patients with the characteristic rash, which is usually the basis for diagnosis. The rash may be confused with that of other viral skin infections.
If the diagnosis is in doubt, laboratory confirmation can be done; it requires one of the following:
Polymerase chain reaction (PCR) for viral DNA
Immunofluorescent detection of viral antigen in lesions
In serologic tests, detection of IgM antibodies to varicella-zoster virus (VZV) or seroconversion from negative to positive for antibodies to VZV indicate acute infection.
Samples are generally obtained by scraping the base of lesions and are transported to the laboratory in viral media. A Tzanck smear of a superficial scraping from the base of a freshly ruptured vesicle stained with Wright-Giemsa or toluidine blue stain demonstrates multinucleated giant cells and epithelial cells with eosinophilic intranuclear inclusion bodies in herpes simplex and herpes zoster infection. Culture can be used but has lower sensitivity than PCR and a long turnaround time (1 to 2 weeks).
Prognosis for Chickenpox
Chickenpox in children is rarely severe. Severe or fatal disease is more likely in the following:
Patients with depressed T-cell immunity (eg, lymphoreticular cancer)
Those receiving corticosteroids or chemotherapy or who are otherwise immunosuppressed
Patients being treated with tumor necrosis factor (TNF) antagonists
Treatment of Chickenpox
Sometimes oral antiviral agents
IV acyclovir for immunocompromised patients and others at risk of severe disease
Mild cases of chickenpox in children require only symptomatic treatment. Relief of itching and prevention of scratching, which predisposes to secondary bacterial infection, may be difficult. Wet compresses or, for severe itching, systemic antihistamines and colloidal oatmeal baths may help.
To prevent secondary bacterial infection, patients should bathe regularly and keep their underclothing and hands clean and their nails clipped. Antiseptics should not be applied unless lesions become infected; bacterial superinfection is treated with antibiotics.
Patients should not return to school or work until the final lesions have crusted.
Antivirals and chickenpox
Oral antivirals, when given to immunocompetent patients within 24 hours of the rash’s onset, slightly decrease symptom duration and severity. However, because the disease is generally benign in children, antiviral treatment is not routinely recommended.
Oral valacyclovir, famciclovir, or acyclovir should be given to healthy people at risk of moderate to severe disease, including patients
12 years of age or older (18 years of age or older for famciclovir)
With skin disorders (particularly eczema)
With chronic lung disease
Receiving long term salicylate therapy
The dose is famciclovir 500 mg 3 times a day or valacyclovir 1 g 3 times a day for adults. Acyclovir is a less desirable choice because it has poorer oral bioavailability, but it can be given at 20 mg/kg 4 times a day for 5 days for children ≥ 2 years and ≤ 40 kg. The dose for children > 40 kg and adults is 800 mg 4 times a day for 5 days.
Immunocompromised children > 1 year should be given acyclovir10 mg/kg every 8 hours IV. Immunocompromised adults should be treated with acyclovir 10 to 12 mg/kg IV every 8 hours.
Because pregnant women are at high risk of varicella complications, some experts recommend oral acyclovir or possibly valacyclovir for pregnant women with varicella. Although available safety data are reassuring, the safety of antiviral therapy during pregnancy is not firmly established, and there is longer experience with acyclovir in pregnancy compared to valacyclovir. Acyclovir and valacyclovir are pregnancy category B drugs. IV acyclovir is recommended for serious varicella disease in pregnant women. There are little data regarding the safety of famciclovir in pregnancy so it is not generally recommended for pregnant women.
Prevention of Chickenpox
Infection provides lifelong protection.
Potentially susceptible people should take strict precautions to avoid people capable of transmitting the infection.
A live-attenuated varicella vaccine Varicella Vaccine Varicella vaccination provides effective protection against varicella (chickenpox). It is not known how long protection against varicella lasts. But, live-virus vaccines, like the varicella... read more is available in 3 formulations in the US:
Standard dose varicella vaccine
Combination measles-mumps-rubella-varicella (MMRV) vaccine
Higher dose vaccine used to prevent herpes zoster (see herpes zoster vaccine Herpes Zoster Vaccine Chickenpox (varicella) and shingles ( herpes zoster) are caused by the varicella-zoster virus; chickenpox is the acute invasive phase of the virus, and shingles represents reactivation of the... read more )
All healthy children and susceptible adults should receive 2 doses of live-attenuated varicella vaccine ( see Table: Recommended Immunization Schedule for Ages 0–6 Years Recommended Immunization Schedule for Ages 0–6 Years and Recommended Immunization Schedule for Ages 7–18 Years Recommended Immunization Schedule for Ages 7–18 Years ). Vaccination is particularly important for women of child-bearing age, those at high risk for exposure, and those who have contact with individuals at higher risk for severe disease. These include healthcare professionals, teachers, child care workers, and residents and staff of nursing homes or other institutional settings. Serologic testing to determine immune status before vaccination in adults is usually not required. Rarely the vaccine may cause chickenpox lesions in immunocompetent patients, but disease is usually mild (< 10 papules or vesicles) and brief and causes few systemic symptoms.
Vaccination of health care workers who do not have evidence of varicella immunity is recommended. Susceptible health care workers who have been exposed to varicella should be vaccinated as soon as possible and kept off duty for 21 days.
Vaccination is contraindicated in
Patients with moderate to severe acute concurrent illness (vaccination is postponed until illness resolves)
Pregnant women and those who intend to become pregnant within 1 month of vaccination (based on Centers for Disease Control and Prevention recommendations) or within 3 months of vaccination (based on vaccine labeling)
Patients taking high doses of systemic corticosteroids
Children using salicylates
After exposure, chickenpox can be prevented or attenuated by intramuscular (IM) administration of varicella-zoster immune globulin (VariZIG). Candidates for postexposure prophylaxis include
People with leukemia, immunodeficiencies, or other severe debilitating illness
Susceptible pregnant women
Neonates whose mother developed chickenpox within 5 days before or 2 days after delivery
Neonates born at < 28 weeks and exposed to a nonmaternal source even if their mother has evidence of immunity (exposed neonates born at ≥ 28 weeks should receive immune globulin if their mother has no evidence of immunity)
The VariZIG immune globulin should be given as soon as possible (and within 10 days of exposure) and may modify or prevent varicella.
Vaccination should be given as soon as possible to exposed, susceptible healthy patients eligible for vaccination (eg, age ≥ 1 year and no contraindications). Vaccination can be effective in preventing or ameliorating disease within 3 days and possibly up to 5 days after exposure.
To prevent nosocomial transmission, the Centers for Disease Control and Prevention recommends postexposure prophylaxis with vaccination or varicella-zoster immunoglobulin, depending on immune status, for exposed health care workers and patients without evidence of immunity (available at Immunization of Health-Care Personnel).
Chickenpox causes pustular, crusting lesions on the skin (often including scalp) and may cause ulcerated lesions on mucous membranes.
Complications include secondary bacterial infection of skin lesions, pneumonia, cerebellar ataxia, and, in adults, encephalitis.
Give oral valacyclovir to varicella patients ≥ 12 years, or famciclovir to varicella patients ≥ 18 years and to those with skin disorders (particularly eczema) or chronic lung disease.
Give IV acyclovir to immunocompromised patients and to other patients at risk of severe disease.
Vaccinate all healthy children and susceptible adults.
Give postexposure prophylaxis with varicella-zoster immune globulin to immunocompromised patients, susceptible pregnant women, and neonates whose mother developed chickenpox within 5 days before or 2 days after delivery.
Give postexposure prophylaxis with varicella vaccine to immunocompetent patients ≥ 1 year who are eligible for vaccination.