Published on 18/03/2015 by admin
Filed under Dermatology
Last modified 18/03/2015
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Christine Soon and John Berth-Jones
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Varicella, or chickenpox, is the exanthematic illness caused by infection with the herpes virus varicella zoster (VZV). Varicella has a typical incubation period of 10 to 14 days, spreading by direct person-to-person contact or by airborne droplets. The disease is infectious from 48 hours before the rash appears until the vesicles crust.
Varicella occurs most commonly in young children. Systemic symptoms are usually mild, although complications may occur. In adolescents, adults, and immunocompromised individuals of any age it is a more severe disease with a higher complication rate. Treatment is most commonly recommended in this group of individuals. Potential complications include secondary bacterial infection of the skin, bacterial pneumonia, and varicella pneumonitis. Rare complications of varicella include aseptic meningitis, encephalitis, cerebellar ataxia, myocarditis, corneal lesions, nephritis, arthritis, acute glomerulonephritis, Reye’s syndrome, bleeding diathesis, and hepatitis. Herpes zoster (shingles), a delayed complication of varicella, is the subject of a separate chapter.
In the US a routine, two-dose, live, attenuated vaccine program of all healthy persons 12 months of age or older who have not had varicella is now recommended. The first dose is administered at age 12–15 months and the second dose at age 4–6 years. A second dose catch-up vaccination is recommended for those who had previously received one dose, including children, adolescents, and adults. Post-exposure immunization may also be effective for household contacts if given within 3 days of the appearance of the rash in the index case. In the UK, vaccination is recommended for non-immune healthcare workers and other carers who are in frequent contact with individuals (mainly immunocompromised patients) who would be especially vulnerable to the infection, the purpose being to protect these vulnerable individuals.
In healthy children below the age of 12 years, symptomatic treatment is all that is generally required. Acetaminophen (paracetamol) is suitable. Aspirin should be avoided because of the risk of Reye’s syndrome. If a child is the second affected case in a family the illness can run a more severe course and antiviral therapy should be considered. Oral acyclovir is the antiviral of choice and should be started within 24 hours of the rash developing.
In healthy adolescents and adults, oral acyclovir commenced within 24 hours of development of the rash has been shown to be beneficial. Heavy smokers and people with chronic lung disease are at greater risk of developing complications, particularly varicella pneumonitis. Treatment with acyclovir should be given if they are seen within 24 hours of the rash developing. There is no evidence to suggest significant benefit if treatment is started after 24 hours in cases where infection is following the normal course and there are no complications. These patients should be treated symptomatically and advised to return promptly if they deteriorate. Patients with complications require hospital assessment.
Pregnant women are more likely to develop severe or complicated disease. Those who are not immune to varicella should avoid contact with varicella and zoster, and if this occurs they should report the contact immediately. Non-immune pregnant women who have had contact with a person with varicella should receive specific varicella zoster immune globulin (VZIG). VZIG is effective up to 10 days after contact. This has been shown to prevent varicella or modify disease severity. It also reduces the risk of fetal transmission if disease develops. Fetal infection between 3 and 28 weeks’ gestation may cause the fetal varicella syndrome (including developmental abnormalities of the eyes and central nervous system). This occurs in an estimated 0.91% of pregnancies complicated by chickenpox during the first 20 weeks of gestation. The risk is probably greatest when infection occurs between 13 and 20 weeks. During the first trimester the use of acyclovir carries a theoretical risk of possible teratogenesis, although it is not a recognized teratogen. Beyond 20 weeks’ gestation, oral acyclovir can be unequivocally recommended if the patient is seen within 24 hours of the onset of the rash. Pregnant women who are smokers, have chronic lung disease, are taking steroids, or are in the latter half of pregnancy are at greater risk of developing systemic symptoms. Hospitalization should be considered in late pregnancy and in women with chest or neurological symptoms, a hemorrhagic rash, bleeding, or very severe disease with a dense rash and mucosal lesions.
Neonates whose mothers had varicella 7 days before to 7 days after delivery should be given prophylaxis with VZIG. Neonates with varicella whose mothers developed varicella within 7 days prior to delivery may develop severe disease and should be treated with intravenous acyclovir. Treatment should also be considered within 48 hours of development of the rash in other infants with congenital varicella (rash within 16 days of delivery) and severe clinical disease.
Immunocompromised individuals exposed to varicella should be given prophylactic VZIG. It is most effective when given within 72 hours, but may still modify disease if given up to 10 days after exposure. All immunocompromised and immunodeficient patients who develop varicella, including those on oral corticosteroids or with a history of oral corticosteroid intake for more than 3 weeks in the preceding 3 months, should be admitted to hospital and treated with intravenous acyclovir, as they are at risk of severe disease and complications. Resistance to acyclovir can occur in immunocompromised individuals following long-term acyclovir therapy. In patients with proven acyclovir-resistant VZV strains, intravenous foscarnet is currently the antiviral agent of choice.
Newer anti-VZV drugs have been developed. These include valacyclovir, famciclovir, and brivudin, although they are currently only licensed for use in herpes zoster. Additional agents are in development.
Virology on vesicle fluid
Serology on acute and convalescent sera
Kangro HO. In: Parker MT, Collier LH, eds. Topley and Wilson’s Principles of Bacteriology, Virology, and Immunity. London: Edward Arnold, 1999; 227–42.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
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