Rubella
Mild viral exanthem caused by rubella virus (Togaviridae), characterised by low-grade fever, maculopapular rash, and postauricular lymphadenopathy. Primary importance is congenital rubella syndrome (CRS) when infection occurs in early pregnancy, causing cataracts, deafness, and cardiac defects.
Key Facts
- Congenital rubella syndrome (CRS): cataracts, sensorineural deafness, congenital heart defects (PDA, pulmonary stenosis), microcephaly - risk highest if infection in first trimester (>80%)
- Postauricular and suboccipital lymphadenopathy: characteristic and may precede the rash
- Rash: pink, maculopapular, starts on face → trunk → extremities; lasts 3 days (German measles = 3-day measles)
- MMR vaccine: eliminated endemic rubella in the UK; WHO-verified rubella elimination status since 2017
- Arthralgia/arthritis: common in adult women (up to 70%); small joint polyarthritis
- Notifiable disease: must report to local health protection team
- Non-immune pregnant women: urgent rubella IgG and IgM if exposed; consider HNIG if non-immune and exposed before 20 weeks
- Diagnosis: rubella IgM (acute infection) and rubella IgG (immunity); rubella PCR for confirmation
Overview
Key Facts
Rubella is a mild childhood exanthem in most cases but its significance lies in teratogenicity during early pregnancy. The MMR vaccination programme has effectively eliminated endemic rubella in the UK.
Epidemiology
- UK: endemic rubella eliminated (WHO verified 2017); rare imported cases
- Pre-vaccine era: epidemics every 6–9 years; up to 300 CRS cases/year in the UK
- Current UK: <10 confirmed cases/year (mostly imported)
- CRS: extremely rare in UK now (<1 case/year)
Aetiology
- Rubella virus: Togaviridae family, genus Rubivirus; single-stranded RNA
- Transmission: respiratory droplets; incubation 14–21 days
- Infectious: 7 days before to 7 days after rash onset
- Congenital rubella: viraemia during pregnancy → transplacental infection
Pathophysiology
- Virus replicates in nasopharyngeal epithelium → viraemia → rash (immune-mediated)
- In pregnancy: virus crosses placenta → fetal infection → cell damage during organogenesis
- CRS pathogenesis: viral inhibition of cell division, apoptosis, vasculitis in developing organs
- Risk of CRS by gestational age: <12 weeks ~80%; 12–16 weeks ~50%; 16–20 weeks ~25%; >20 weeks minimal risk
Clinical Presentation
Postnatal Rubella
- Low-grade fever
- Postauricular, suboccipital, and posterior cervical lymphadenopathy (precedes rash by 1–5 days)
- Pink maculopapular rash: face → trunk → extremities; lasts ~3 days
- Arthralgia/arthritis: especially adult women (small joints - fingers, wrists)
- Generally mild; 25–50% subclinical
Congenital Rubella Syndrome
- Classic triad: sensorineural deafness, congenital heart defects (PDA, pulmonary stenosis), cataracts/glaucoma
- Additional: microcephaly, intellectual disability, hepatosplenomegaly, thrombocytopenia (blueberry muffin baby), radiolucent bone disease
- Infant may excrete virus for months (contagious)
Red Flags
- Rubella exposure in non-immune pregnant woman (especially <20 weeks)
- Rash illness in early pregnancy
- Neonate with cataracts + heart murmur + deafness
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Measles | Higher fever, 3 Cs, Koplik spots, more unwell | Measles IgM/PCR |
| Parvovirus B19 | Slapped cheek, reticular rash, arthropathy | Parvovirus IgM |
| Scarlet fever | Sandpaper rash, strawberry tongue, pharyngitis | Throat swab, ASO titre |
| Drug eruption | Temporal drug relationship | Drug history |
| Enteroviral exanthem | Various rash patterns, hand-foot-mouth | Enterovirus PCR |
| EBV | Tonsillar exudate, splenomegaly, atypical lymphocytes | Monospot, EBV serology |
Diagnosis / Investigation
Bloods
- Rubella IgM: positive in acute infection (detectable from rash onset, peaks at 1–2 weeks)
- Rubella IgG: seroconversion or 4-fold rise in paired sera confirms acute infection; positive IgG indicates immunity
- Rubella PCR: throat swab or urine - for confirmation and genotyping
- FBC: mild thrombocytopenia, leucopenia
In Pregnancy
- Rubella IgG: check immune status (antenatal booking blood)
- If exposed and non-immune: urgent rubella IgM and IgG; repeat at 2–3 weeks
- Amniocentesis: rubella PCR on amniotic fluid if maternal infection confirmed (after 15 weeks)
Congenital Rubella
- Rubella IgM in neonate: indicates congenital infection (does not cross placenta)
- Rubella PCR: on infant blood, urine, throat swab
- Ophthalmology: cataracts, glaucoma
- Audiology: sensorineural deafness
- Echocardiography: PDA, pulmonary stenosis
- Cranial USS/MRI: microcephaly, calcification
Management
Non-pharmacological
- Supportive care: rest, fluids, paracetamol for fever/arthralgia
- Isolation: 7 days after rash onset; keep away from pregnant women
- Notification: statutory notification
- Contact tracing: identify susceptible pregnant contacts
Pharmacological
- No specific antiviral treatment
- HNIG (human normal immunoglobulin): may be offered to non-immune pregnant women exposed before 20 weeks - does NOT prevent infection but may reduce severity
- Post-exposure MMR: not recommended in pregnancy (live vaccine contraindicated)
- Arthralgia: NSAIDs (not in pregnancy)
Vaccination
- MMR vaccine: 2 doses in childhood; catch-up for non-immune women of childbearing age
- Post-partum vaccination: offer MMR to non-immune women after delivery (avoid pregnancy for 1 month after)
- Live vaccine: contraindicated in pregnancy and immunocompromised
Referral Criteria
- Fetal medicine: if rubella infection confirmed in pregnancy - discuss options including termination if first-trimester infection
- Paediatrics: CRS management (multidisciplinary - cardiology, ophthalmology, audiology)
- Public health: all cases
Prognosis
- Postnatal rubella: excellent prognosis, self-limiting in 3–5 days
- Arthritis: self-limiting in 2–4 weeks; chronic arthritis rare
- CRS first trimester infection: >80% risk of fetal abnormalities
- CRS second trimester: ~25% risk (mainly deafness)
- CRS after 20 weeks: minimal risk
- CRS infant: lifelong disabilities in most cases
- Deafness in CRS: most common single defect (~60–75%)
- CRS mortality in infancy: ~10–20% in severe cases
Other Relevant Information
Congenital Rubella Syndrome Features
| System | Manifestations |
|---|---|
| Eye | Cataracts, microphthalmos, glaucoma, retinopathy |
| Ear | Sensorineural deafness (most common) |
| Heart | PDA (most common cardiac), pulmonary stenosis, VSD |
| CNS | Microcephaly, intellectual disability, meningoencephalitis |
| Haematological | Thrombocytopenia, anaemia (blueberry muffin baby) |
| Other | Hepatosplenomegaly, IUGR, radiolucent bone disease |
Risk of CRS by Gestational Age
| Gestational Age | Risk of Fetal Infection | Risk of Defects |
|---|---|---|
| <12 weeks | >80% | >80% |
| 12–16 weeks | ~50% | ~50% (mainly deafness) |
| 16–20 weeks | ~25% | ~25% (deafness) |
| >20 weeks | Minimal | Minimal |