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 |