Varicella and herpes zoster — formative SAQs

SAQ 1 (10 marks)

A 6-year-old boy receiving maintenance chemotherapy for acute lymphoblastic leukaemia is brought to the emergency department with a 24-hour history of fever and a generalised vesicular rash that began on the trunk. His sibling had chickenpox two weeks ago. The child is febrile to 38.9 °C, tachypnoeic, and has lesions in all stages across his trunk and face. ^[1]

Question: Outline the immediate and stepwise management of this child, including risk stratification, investigations, treatment, infection control and the public-health response. (10 marks) ^[3]

Model answer

Risk stratification and disposition (2 marks). This child is a high-risk host — an immunocompromised patient on chemotherapy — and primary varicella in this group carries a real risk of disseminated, fulminant disease. Admit promptly, and have a low threshold for a monitored bed or PICU involvement given his tachypnoea. The host-risk tier is the organising principle: he needs urgent intravenous aciclovir, not the supportive default applied to a healthy child. ^{[1] [3]}

Investigations (2 marks). Confirm with PCR of vesicle fluid or a lesion-base swab, which is the test of choice for atypical, severe or high-risk cases, and which can distinguish wild-type from vaccine-strain virus. Given his tachypnoea, request a chest X-ray to look for varicella pneumonia, and check liver function tests and a coagulation screen to assess for hepatitis and disseminated disease. Do not delay treatment while waiting for results. ^[1]

Treatment (3 marks). Start intravenous aciclovir promptly without waiting for PCR confirmation when the clinical picture is compelling — delaying antiviral therapy in a host who cannot contain the virus is the avoidable error. Maintain hydration carefully to protect against aciclovir-induced nephrotoxicity. If pneumonia, secondary bacterial infection or invasive group A streptococcal disease emerges, add the appropriate targeted therapy — antibiotics covering streptococcus and staphylococcus including clindamycin for toxin suppression, and surgical review for necrotising fasciitis. Paracetamol for fever; never aspirin or salicylates because of the Reye syndrome association. ^{[3] [1]}

Infection control and public health (3 marks). Place the child under airborne plus contact precautions, because the virus spreads by both routes. Notify public health according to local requirements, because varicella is notifiable. Identify all high-risk contacts — pregnant women, neonates, immunocompromised individuals, and non-immune siblings or classmates — and arrange post-exposure prophylaxis. For contacts in whom the live vaccine is not contraindicated, give varicella vaccine within three to five days of exposure; for high-risk contacts in whom it is contraindicated (pregnant, neonate, immunocompromised), give varicella-zoster immune globulin. The encounter is not over until the contacts have been protected. ^{[2] [5]}