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]

SAQ 2 (10 marks)

Question: A 15-year-old girl who is 24 weeks pregnant is seen in the clinic two days after her unvaccinated younger brother developed chickenpox. She has no history of chickenpox and no documented varicella vaccination. She is currently well with no rash. (a) How will you assess and manage her exposure? (b) If she develops primary varicella, what are the risks to her and to the fetus, and how would you manage the illness? (c) How could this have been prevented? (10 marks) [5]

Model answer

(a) Assessment and management of the exposure (3 marks). Determine her immune status first. In the absence of a reliable history or documented vaccination, check varicella IgG serology. If she is non-immune, she is a high-risk contact and should receive varicella-zoster immune globulin (VZIG) promptly to prevent or modify maternal disease and its complications — the live varicella vaccine is contraindicated in pregnancy. Counsel her to watch for rash and respiratory symptoms and to present immediately if she becomes unwell, because varicella pneumonia is the feared maternal complication and is more severe in pregnancy. [5] [2]

(b) Risks if she develops primary varicella, and management (4 marks). The maternal risk is varicella pneumonia, which is more severe in pregnancy and is the leading cause of varicella death in adults; it presents with cough, dyspnoea, tachypnoea and hypoxia. The fetal risk depends on gestation: at 24 weeks she is within the window where primary maternal infection carries a small risk of congenital varicella syndrome — limb hypoplasia, skin scarring, eye abnormalities and neurological deficits. If she develops varicella, admit and start intravenous aciclovir promptly, especially if any respiratory symptoms appear; the threshold to treat aggressively is lowest in pregnancy. Involve obstetrics and the neonatal team for fetal surveillance and forward planning. [5] [1]

(c) Prevention (3 marks). Prevention rests on pre-pregnancy vaccination. The two-dose live varicella vaccine should be given before conception, because it is contraindicated in pregnancy, and pregnancy should be avoided for a month after vaccination. Verifying and completing immunisation status as part of pre-conception and adolescent care is the durable protection. Around her, household and community vaccination protects the susceptible pregnant woman by reducing circulation. The lesson is that every opportunity to immunise before pregnancy prevents exactly this scenario — the pregnant non-immune adolescent exposed to a household case. [1] [2]