Varicella is a viral illness caused by varicella-zoster virus (VZV) and characterized by the acute onset of a generalized vesicular rash and fever.¹

Chickenpox

• Varicella is extremely contagious. Approximately 60% to 90% of unvaccinated contacts become infected.
• Before the vaccine, ∼95% of children under the age of 5 were infected by VZV.¹
• Transmission is via respiratory droplets, aerosolized vesicular contents, or direct contact with skin lesions.²
• The incubation period of chickenpox ranges from 7 to 21 days.
• The peak incidence is late winter and early spring.
• The contagious period begins 2 days before the onset of clinical symptoms and lasts until all of the lesions have crusted, an average of 7 days.

Approximately 3% of children may develop a benign varicella-like rash 5 to 26 days after vaccination.¹

• Most patients will have lifelong immunity after contracting chickenpox; protection from the virus after a varicella vaccine is approximately 5 years and is more effective with a two-dose regimen.³
• After infection, VZV becomes latent in the sensory ganglia, with reactivation with herpes zoster (shingles) possibly decades later.²
• Primary maternal VZV during first or early second trimester causes congenital varicella syndrome in up to 25% of cases.⁴

• Findings vary with the clinical course. Initial symptoms consist of fever, chills, backache, generalized malaise, and headache.
• Children present with discomfort and malaise, while adolescents and adults are at risk for severe infection. Initial lesions generally occur on the head and face, trunk (centripetal distribution), and then extremities, but can appear anywhere, including mucous membranes.
• These lesions consist primarily of 3- to 4-mm red papules with an irregular outline that develop into clear vesicles with an erythematous base (Fig. E1) (i.e., the appearance of “dewdrops on a rose petal”).
• Intense pruritus generally accompanies the initial stage. Excoriations may be present if scratching is prominent.
• The fever is usually highest during the eruption of the vesicles; the patient’s temperature generally returns to normal after the disappearance of vesicles.
• New lesion development generally ceases by the fourth day, with subsequent umbilication and crusting by the sixth day.
• Lesions in varying stages of healing is a hallmark feature.
• Crusts generally fall off within 5 to 14 days. Scarring may occur in association with secondary bacterial infections (Figs. E2 and E3).
• Skin lesions may become superinfected by bacteria, including Streptococcus pyogenes (Group A strep) or Staphylococcus aureus.
• Signs of potential complications (e.g., bacterial skin infections, neurologic complications, pneumonia, hepatitis) may be present on physical examination. Acute cerebellar ataxia is the most common extracutaneous complication.

Varicella-zoster virus (VZV) is a double-stranded DNA, human herpes virus III (HHV-3) that can manifest with either primary infection (varicella) or herpes zoster (i.e., shingles, which is a reactivation of latent varicella).¹

• Other viral infection (i.e., coxsackievirus, herpes simplex virus)
• Impetigo
• Scabies
• Drug rash
• Urticaria
• Dermatitis herpetiformis
• Smallpox
• Stephen-Johnson syndrome

The diagnosis is usually made on the basis of the patient’s history and clinical presentation.

• Laboratory evaluation is generally not necessary.
• CBC may reveal leukopenia and thrombocytopenia.
• Serum varicella titers (i.e., a significant rise in the serum varicella immunoglobulin G antibody level), skin biopsies, or Tzanck smears are used only when diagnosis is in question.

• Radiography is generally not necessary unless the patient exhibits respiratory distress, tachypnea, or abnormal pulse oximetry readings.
• Chest x-ray examination may show interstitial infiltrates or nodular consolidations in the presence of varicella pneumonia.

• Use antipruritic lotions for symptomatic relief.
• Avoid scratching to prevent excoriations and superficial skin infections.
• Use a mild soap for bathing. Wash hands often to prevent spread of infection.
• Encourage fluid intake to prevent dehydration.

• Use acetaminophen for fever and myalgias; aspirin should be avoided because of the associated increased risk of Reye syndrome.⁵
• Oral acyclovir (20 mg/kg qid for 5 days), valacyclovir, or famciclovir initiated at the earliest sign (i.e., within 24 hr of illness) is useful for children with chronic pulmonary or cutaneous disorders, those receiving long-term aspirin or steroids, pregnant women, and unvaccinated children older than 12 yr to decrease the duration and severity of signs and symptoms.⁴
• Immunocompromised hosts or those with severe infection should be admitted to the hospital and treated with intravenous acyclovir 500 mg/m² or 10 mg/kg q8h within 24 hr for 7 to 10 days.^2,4,5
• Healthy, nonimmune adults and children who are exposed should receive prophylaxis with live attenuated varicella vaccine (Varivax) within 3 days of exposure. Patients with HIV or other immunocompromised patients should not receive the live vaccine. All pregnant women should be screened for immunity.^5-7
• Exposed patients with contraindications to varicella vaccine can be treated with varicella-zoster immunoglobulin (VariZIG) or IVIG (if VariZIG is not available). VariZIG must be administered as early as possible (i.e., within 96 hr and up to 10 days after exposure). The dose is 12.5 U/kg intramuscularly (IM) up to a maximum of 625 U.^5-8
• Oral antibiotics are not routinely indicated and should be used only in patients with bacterial superinfection.

• The course is generally self-limited in immunocompetent adults and children.
• Once all lesions have crusted, children may return to school.

• VariZIG can be obtained from the nearest regional Red Cross Blood Center or the Centers for Disease Control and Prevention in Atlanta.
• Varicella immunization is recommended for all children ages 1 to 12 yr and those >13 with no immunity.

Chickenpox (Patient Information)