Measles, rubella and congenital rubella — formative SAQs

SAQ 1 (10 marks)

A 4-year-old unvaccinated child is brought to the emergency department with four days of fever, coryza, cough and red, watery eyes. This morning a blotchy red rash appeared behind the ears and is now spreading down the trunk. On examination the child is febrile to 39.5 °C, miserable, with conjunctivitis and small white lesions on an erythematous buccal mucosa. There are scattered crackles at the right base. The family recently returned from a region with an ongoing measles outbreak. [5]

Question: Outline the immediate and stepwise management of this child, including diagnosis, treatment, supportive care, infection control and the public-health response. (10 marks) [1]

Model answer

Recognition and disposition (2 marks). This is classic measles — the 3 C's (cough, coryza, conjunctivitis), Koplik spots on the buccal mucosa, a cephalocaudal maculopapular rash in an unvaccinated child with an exposure history. Isolate immediately with airborne precautions. The basal crackles raise pneumonia — the commonest cause of measles death — so admit for monitoring, oxygen and supportive care, with a low threshold for escalation if work of breathing rises. [5]

Diagnosis (2 marks). Confirm with measles-specific IgM on a serum sample taken at first contact (positive from the first day of the rash) plus RT-PCR and genotyping on a throat or nasopharyngeal swab and urine within the first days of the rash. PCR is particularly useful early when IgM may still be negative, and genotyping supports outbreak linkage. Do not delay management while waiting. [1]

Treatment — vitamin A and supportive care (3 marks). Give vitamin A in two age-appropriate doses 24 hours apart — the randomised trial and the Cochrane review confirm it reduces measles mortality and morbidity. Provide supportive care: fluids, antipyretics and nutrition; treat secondary bacterial pneumonia with antibiotics if present; protect the eyes and watch for corneal ulceration. Give oxygen for hypoxia and escalate to intensive care if the respiratory status deteriorates. [4] [9]

Infection control and public health (3 marks). Maintain airborne precautions and exclude from school or childcare until four days after the rash onset. Notify public health on suspicion — do not wait for confirmation — which triggers contact tracing. Identify susceptible contacts (fewer than two documented MMR doses) and offer post-exposure MMR within 72 hours of exposure; give immunoglobulin to high-risk contacts such as pregnant non-immune women, immunocompromised children and infants under protocol. Document onset and rash dates, the infectious period (prodrome to four days after the rash), and exposures. Reinforce catch-up vaccination for the household and counsel the family that immunity to other infections may be impaired for months to years because of measles immune amnesia. [1] [8] [3]

SAQ 2 (10 marks)

Question: A 26-year-old woman at 9 weeks gestation presents with a three-day history of low-grade fever, a fine pink rash spreading from her face downward, and tender postauricular lymph nodes. Her antenatal booking rubella IgG was reported as 'low-positive/equivocal'. (a) What is the likely diagnosis and how will you confirm it? (b) Outline the counselling and management, including the gestation-specific risk. (c) How could this have been prevented, and what is the postpartum plan if she proves non-immune? (10 marks) [6]

Model answer

(a) Diagnosis and confirmation (3 marks). The likely diagnosis is rubella, which is a trivial illness in the mother but a devastating teratogen in the first trimester. Do NOT reassure on clinical grounds — confirm serologically. Check the booking serology, take an acute serum for rubella IgM and IgG immediately, and repeat serology at the appropriate interval if IgM is negative but exposure was recent; a rising IgG or IgM seroconversion confirms infection. PCR on a throat swab can support the diagnosis, and fetal-medicine PCR on amniotic fluid (at the appropriate gestation) can confirm fetal infection once maternal infection is established. [6]

(b) Counselling and management (4 marks). Date the gestation precisely — this is the single most important number, because CRS risk is governed by gestational age at maternal infection. The risk of any defect, and of multiple defects, is approximately 90 per cent at 0 to 11 weeks, falls to around 50 per cent at 12 to 17 weeks (mainly deafness and cardiac disease), and is rare after 18 to 24 weeks. At 9 weeks this woman is in the highest-risk window, so counsel her honestly about the probability and pattern of defects (sensorineural deafness, cataracts, PDA and neurodevelopmental deficit), and involve fetal medicine for amniotic-fluid PCR and detailed anomaly scanning. Support her decision within the medicolegal framework of her jurisdiction. [6]

(c) Prevention and the postpartum plan (3 marks). CRS is entirely preventable through rubella-containing vaccination. Prevention rests on screening every pregnancy for rubella IgG at booking, vaccinating non-immune women postpartum, and sustaining two-dose MMR coverage above 95 per cent so that infection does not circulate and women reach pregnancy immune. MMR is a live vaccine and is contraindicated in pregnancy, so if this woman proves non-immune she should receive MMR postpartum, with advice to avoid pregnancy for the recommended interval after vaccination — protecting the next pregnancy. [8] [6]