Chickenpox

Chickenpox is caused by the varicella-zoster virus, a dermatropic and neurotropic virus. The primary disease occurs in childhood. Can reactivate later.

Spread- aerosol and direct contact. Highly infectious to the non-immune. Well tolerated in children. Severe disease in pregnancy, immunocompromised and adults

Incubation 11-20 days.

Clinical features

• Vesicular rash that starts on mucosal surfaces then rapidly spreads centripetally.
• New lesions every 2 to 4 days; each crop is associated with fever
• Infectivity- 4 days before rash till last vesicles crust over
• Severe disease- that with visceral involvement
• Maternal infection early in the pregnancy carries a 3% risk of developmental abnormality in the eyes, CNS, and limbs. Within five days of delivery, there’s a severe disease with visceral involvement.

Complications

The most common is a 2⁰ bacterial infection from itching.

Others;

• Self-limiting cerebellar ataxia
• Hepatitis, pneumonia
• Encephalitis

Diagnosis

1. Mainly clinical
2. DNA or PCR of fluid- detects antigen
3. Serology- identify those seronegative at risk of infection

Management

1. Supportive- antihistamines, cropping of fingernails, and acetaminophen in children

2. Antivirals- acyclovir or its analogues

Indications; – an uncomplicated disease in adults

• Complicated disease
• The pregnant and immunocompromised
• Acyclovir 800mg 5 times daily for five days
• Intravenous therapy for severe disease
• Prolonged treatment for the immunocompromised

3. Human Varicella Zoster immunoglobulin. For;

• Those susceptible to infection
• Those at risk for severe disease
• Significant contact with the virus

Given within seven days of exposure

Prevention

1. Vaccination;

• Children – at 1yr and 4 to 6 years old
• Seronegative adults- 2 doses, one month apart
• In planned immunosuppression, e.g., transplant.