Chickenpox is caused by the varicella-zoster virus (human herpesvirus type 3); chickenpox is the acute invasive phase of the infection, and herpes zoster (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, chickenpox epidemics occurred in winter and early spring in 3- to 4-year cycles.
(See Overview of Herpesvirus Infections.)
Symptoms and Signs of Chickenpox
In children who are immunocompetent, chickenpox is rarely severe. In adults and children who are immunocompromised, 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 old and is usually more severe in adults.
Initial rash
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.
Image courtesy of Ann Cain via the Public Health Image Library of the Centers for Disease Control and Prevention.
Image courtesy of Renelle Woodall via the Public Health Image Library of the Centers for Disease Control and Prevention.
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.
Breakthrough varicella
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.
Complications
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 patients of all ages who are immunocompromised, but usually not in young children who are immunocompetent.
Myocarditis, hepatitis, and hemorrhagic complications may also occur.
Acute postinfectious cerebellar ataxia is one of the most common neurologic complications in children; it occurs in 1/4000 cases in children younger than 15 years of age (1).
Transverse myelitis may also occur.
In adults, encephalitis can be life threatening.
Symptoms and signs reference
1. Guess HA, Broughton DD, Melton LJ 3rd, Kurland LT: Population-based studies of varicella complications. Pediatrics 78(4 Pt 2):723-727, 1986.
Diagnosis of Chickenpox
History and physical examination
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
Serologic tests
Viral culture
Tzanck smear
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 longer turnaround time (1 to 2 weeks).
Treatment of Chickenpox
Symptomatic treatment
Sometimes oral antiviral agents
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 patients who are immunocompetent 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 of healthy children ≤ 12 years old is not routinely recommended.
1), including patients with any of the following characteristics:
Skin disorders (particularly eczema)
Chronic lung disease
Long-term salicylate therapy
Current corticosteroid therapy
A secondary case contracted from household contacts, because secondary cases are usually more severe than primary cases
Because pregnant women
Treatment reference
1. Committee on Infectious Diseases, American Academy of Pediatrics. Red Book: 2021 – 2024 Report of the Committee on Infectious Diseases. 32nd ed. American Academy of Pediatrics; 2021
Prognosis for Chickenpox
Chickenpox in children is rarely severe. Severe or fatal disease is more likely in the following:
Adults
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
Prevention of Chickenpox
Infection provides lifelong protection.
Potentially susceptible people should take strict precautions to avoid people capable of transmitting the infection.
Vaccination
A live-attenuated varicella vaccine is available in 2 formulations in the United States:
Standard two-dose varicella vaccine
Combination measles-mumps-rubella-varicella (MMRV) vaccine
All healthy children and susceptible adults should receive 2 doses of live-attenuated varicella vaccine (see Centers for Disease Control and Prevention [CDC]: Child and Adolescent Immunization Schedule by Age) (1). 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 (eg, correctional institutions). Serologic testing to determine immune status before vaccination in adults is usually not required. Rarely the vaccine may cause chickenpox lesions in patients who are immunocompetent, 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 who had a severe allergic reaction (eg, anaphylaxis) after a previous dose of the vaccine or to a vaccine component
Patients with moderate to severe acute concurrent illness (vaccination is postponed until illness resolves)
Patients who are immunocompromised
Pregnant women and those who intend to become pregnant within 1 month of vaccination (based on CDC recommendations) or within 3 months of vaccination (based on vaccine labeling)
Patients taking high doses of systemic corticosteroids
Children using salicylates
Postexposure prophylaxis
People with leukemia, immunodeficiencies, or other severe debilitating illness without evidence of immunity
Pregnant women without evidence of immunity
Neonates whose mother developed chickenpox within 5 days before or 2 days after delivery
Neonates born at < 28 weeks and exposed to a non-maternal 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 CDC 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).
Prevention reference
1. Marin M, Güris D, Chaves SS, Schmid S, Seward JF; Advisory Committee on Immunization Practices, Centers for Disease Control and Prevention (CDC): Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 56(RR-4):1-40, 2007.
Key Points
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.
Vaccinate all healthy children and susceptible adults.
Give postexposure prophylaxis with varicella vaccine to patients ≥ 1 year who are immunocompetent and are eligible for vaccination.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of the resources.
