Viral infection in a child: Chickenpox Flashcards
Define chickenpox.
Contagious infectious disease caused by the DNA herpes virus varicella zoster.
Explain the aetiology of antenatal chickenpox.
Varicella embryopathy (VE) is caused by transplacental transmission during maternal infection in 2.2% of foetuses if < 20 weeks’ gestation.
Explain the aetiology of perinatal chickenpox.
Varicella of the newborn (VON); severity depends on the time of maternal infection:
- 21-5 days before delivery: VON appears in first 4 days and there is a good prognosis.
- 5 days before delivery or 2 days after delivery: VON presents day 6-26; may be mild or severe (30% mortality).
Explain the aetiology of postnatal chickenpox.
Transmission via the respiratory route; preterm infants are at higher risk due to lack of placental varicella IgG transfer in the third trimester.
Explain the aetiology of childhood chickenpox.
Virus enters the respiratory tract and undergoes replication in the regional lymph nodes. At 4-6 days a primary viraemia spreads the virus to the reticuloendothelial cells primarily in the spleen and liver. At 11-24 days there is a secondary viraemia to the viscera and skin, which elicits typical skin lesions.
What are risk factors for chickenpox?
Maternal
Family contact
School contact with infected individuals
Summarise the epidemiology of chickenpox.
15% of pregnant women are susceptible to varicella infection.
Incidence of varicella during pregnancy is 3/1000 in the UK. Household transmission rates are 80-90%.
What are signs and symptoms of varicella embryopathy?
CNS: Microcephaly, paralysis, developmental delay, seizures.
Ocular: Cataracts, chorioretinitis, microphthalmia, nystagmus.
Musculoskeletal: Cicatricial dermatomal skin lesions and scarring, unilateral atrophy of a limb with scarring and paresis, rudimentary digits.
What are signs and symptoms of varicella of the newborn?
- Prodrome: Poor feeding, mild pyrexia and malaise.
- Rash: Morbiliform rash in the prodrome develops into a generalized pruritic vesicular rash.
What are signs and symptoms of childhood chickenpox?
Prodrome: Mild pyrexia precedes skin manifestation by 1-2 days.
Rash: Appears in crops at different stages (papule, vesicle, pustule and crust). Varicella’s hallmark is the simultaneous presence of different stages of skin lesions and intense pruritus.
Systemic: Abdominal pain, headache, malaise, anorexia, cough, coryza, sore throat.
What are appropriate investigations for chickenpox?
Varicella infection is usually a clinical diagnosis.
Specific test: Serology (varicella-specific IgM) in fetal blood, detection of varicella antigens by ELISA, virology from vesicular fluid.
What is the management of chickenpox?
Conservative: Cool compresses, calamine lotion, regular bathing to manage pruritus, discourage scratching to prevent scarring (mittens may be necessary).
Medical: Sedating antihistamines for pruritus, acyclovir is indicated for moderate to severe disease.
When is varicella Ig indicated?
Infants born to mothers with infection 5 days before delivery or 2 days after.
At-risk infants (<28 weeks or < 1000 grams).
Exposed seronegative pregnant women.
How is chickenpox prevented?
Routine VZ immunisation is available in some countries (USA, Canada, Germany, Australia, Uruguay).
What are complications associated with chickenpox?
In childhood varicella 1/50 cases are associated with complications.
Neurological: Meningoencephalitis, encephalitis, acute cerebellar ataxia, Reye syndrome.
Skin: Impetigo (most common complication), scarring, necrotising fasciitis.
Other: Pneumonia, GN, myocarditis, pancreatitis, HSP.
