Chickenpox risk factors

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Michael Maddaleni, B.S.

Risk Factors

High Risk Patients

Although all susceptible patients in health care settings are at risk for severe varicella and complications, certain patients without evidence of immnunity are at increased risk:

• Pregnant women.
• Premature infants born to susceptible mothers.
• Infants born at less than 28 weeks gestation or who weigh ≤1000 grams regardless of maternal immune status.
• Immunocompromised persons (including those who are undergoing immunosuppressive therapy, have malignant disease, or are immunodeficient).

Immunocompromised patients

Immunocompromised persons who get varicella are at risk of developing visceral dissemination (VZV infection of internal organs) leading to pneumonia, hepatitis, encephalitis, and disseminated intravascular coagulopathy. They can have an atypical varicella rash with more lesions, and they can be sick longer than immunocompetent persons who get varicella. The lesions may continue to erupt for as long as 10 days, may appear on the palms and soles, and may be hemorrhagic.

People with HIV or AIDS

Children with HIV infection tend to have atypical rash with new crops of lesions presenting for weeks or months. HIV-infected children may develop chronic infection in which new lesions appear for more than one month. The lesions may initially be typical maculopapular vesicular lesions but can later develop into non-healing ulcers that become necrotic, crusted, and hyperkeratotic. This is more likely to occur in HIV-infected children with low CD4 counts.

Some studies have found that VZV dissemination to the visceral organs is less common in children with HIV than in other immunocompromised patients with VZV infection. The rate of complications may also be lower in HIV-infected children on antiretroviral therapy or HIV-infected persons with higher CD4 counts at the time of varicella infection. Retinitis can occur among HIV-infected children and adolescents.

Most adults, including those who are HIV-positive have already had varicella disease and are VZV seropositive. As a result, varicella is relatively uncommon among HIV-infected adults.

Neonates

Varicella infection in pregnant women can lead to viral transmission via the placenta and infection of the fetus. If infection occurs during the first 28 weeks of gestation, this can lead to fetal varicella syndrome (also known as congenital varicella syndrome). Effects on the fetus can range in severity from underdeveloped toes and fingers to severe anal and bladder malformation. Possible problems include:

• Damage to brain: encephalitis, microcephaly, hydrocephaly, aplasia of brain
• Damage to the eye (optic stalk, optic cap, and lens vesicles), microphthalmia, cataracts, chorioretinitis, optic atrophy
• Other neurological disorder: damage to cervical and lumbosacral spinal cord, motor/sensory deficits, absent deep tendon reflexes, anisocoria/Horner's syndrome
• Damage to body: hypoplasia of upper/lower extremities, anal and bladder sphincter dysfunction
• Skin disorders: (cicatricial) skin lesions, hypopigmentation

Infection late in gestation or immediately post-partum is referred to as neonatal varicella. Maternal infection is associated with premature delivery. The risk of the baby developing the disease is greatest following exposure to infection in the period 7 days prior to delivery and up to 7 days post-partum. The neonate may also be exposed to the virus via infectious siblings or other contacts, but this is of less concern if the mother is immune. Newborns who develop symptoms are at a high risk of pneumonia and other serious complications of the disease.

Pregnant Women

Pregnant women who get varicella are at risk for serious complications; they are at increased risk for developing pneumonia, and in some cases, may die as a result of varicella.

If a pregnant woman gets varicella in her 1st or early 2nd trimester, her baby has a small risk (0.4 – 2.0 percent) of being born with congenital varicella syndrome. The baby may have scarring on the skin, abnormalities in limbs, brain, and eyes, and low birth weight.

If a woman develops varicella rash from 5 days before to 2 days after delivery, the newborn will be at risk for neonatal varicella. In the absence of treatment, up to 30% of these newborns may develop severe neonatal varicella infection.

Infants without Passive Immunity

Children under one year of age whose mothers have had chickenpox are not very likely to catch it. If they do, they often have mild cases because they retain partial immunity from their mothers' blood. Children under one year of age whose mothers have not had chickenpox, or whose inborn immunity has already waned, can get severe chickenpox.