Description

Rubella is usually a mild, self-limiting viral infection. Its major complication of maternal infection in early pregnancy is congenital rubella syndrome (CRS).

CRS is an entirely preventable disease.

Epidemiology

• Rubella is now a very uncommon infection in the UK as a result for the vaccination programme.
• However, rubella is still common in many developing countries.
• There was only one documented case of rubella in the UK in 2011.^[1]
• National uptake of antenatal screening for rubella susceptibility increased from 94% in 2005 to 97% in 2010.^[2]

Presentation

In the mother

See separate Rubella article.

• Rubella has an incubation period of 14-21 days.
• It is usually a self-limiting illness.
• There is usually a prodromal phase of lassitude, low-grade fever, mild conjunctivitis and coryzal symptoms.
• Often present are macular rash and posterior auricular lymphadenopathy.
• Arthralgia, affecting mostly the wrist and joints of the hand, can also occur.
• There is very little malaise in children but adults tend to feel more unwell.
• It may cause first-trimester miscarriage.
• 20-50% of all rubella infections are subclinical. Re-infection is possible but the immune response is modified and the risk to the fetus is low.

In the baby

• Infection in the first 8-10 weeks of pregnancy results in damage in up to 90% of surviving infants. Multiple defects are then common.
• The risk of damage reduces to 10-20% if the infection is in the first 11-16 weeks of pregnancy.
• Fetal damage is rare over 16 weeks of gestation.

• Transient:
  • Intrauterine growth restriction.
  • Thrombocytopenic purpura (25% - 'blueberry skin').
  • Haemolytic anaemia.
  • Hepatosplenomegaly.
  • Jaundice (common).
  • Radiolucent bone disease (20%).
  • Meningoencephalitis (25%) +/- neurological sequelae.
• Developmental:
  • Sensorineural deafness (80%, variable, unilateral or bilateral) - rubella is the most common cause of congenital deafness in the developed world.
  • Mental retardation (55%).
  • Insulin-dependent diabetes (20%, immune-mediated, but often delayed to adolescence or adulthood).
  • 'Late-onset' disease at 3-12 months with rash, diarrhoea, pneumonitis and high mortality.
• Permanent:
  • Congenital heart disease (commonly patent ductus arteriosus or peripheral pulmonary artery stenosis).
  • Eye defects including cataracts, congenital glaucoma, pigmentary retinopathy (50% - so-called 'salt and pepper'), severe myopia, microphthalmia.
  • Microcephaly.

Differential diagnosis

A number of viruses can cause a rubella-like rash and, so when an accurate diagnosis is imperative, as in early pregnancy, laboratory investigations must be undertaken.

In pregnancy, rubella is indistinguishable from parvovirus B19. Due to the wide differential and potential fetal risks, it is important to seek advice/follow Health Protection Agency (HPA) guidance on rash illness and exposure to rash illness during pregnancy.^[3]

The other viruses in the TORCH group (= toxoplasmosis, rubella, cytomegalovirus, herpes simplex) have the following common features:

• Preterm delivery.
• Low birthweight.
• Anaemia.
• Thrombocytopenia.
• Hepatitis with jaundice and hepatosplenomegaly.
• Microcephaly, mental handicap, seizures, and failure to thrive.

Investigations

If a pregnant woman is suspected of having rubella, the clinical diagnosis is very unreliable.

Detection of specific IgM in saliva samples is both sensitive and specific:

• Rubella-specific IgM implies primary infection.
• A rise in IgG titre over two weeks usually occurs.
• The rubella virus can potentially be isolated from a throat culture during the acute phase of illness, but this technique is not a practical way to establish the diagnosis.^[4]

Criteria for postnatal diagnosis in the baby:

• IgM antibodies do not cross the placenta and indicate a recent infection acquired after birth.
• Unexpected persistence of rubella IgG (does not drop at two-fold dilution/month as maternal IgG does - which is cleared by six months).
• PCR is a very sensitive test for the virus.^[5]

Management

A termination of pregnancy is usually offered if there is positive IgM in the first 16 weeks of pregnancy.

• The need for special educational provision will depend on the presence/combination of mental handicap, hearing and visual defects. These should be assessed at the earliest opportunity.
• Cochlear implants are showing some success.
• Cardiac surgery may be required.

Prognosis

Prognosis depends upon the severity of the lesions, the combinations of defects present and the quality of the input to the child.

Prevention

Prevention is based on a programme of immunisation:

• Prevention of congenital rubella syndrome (CRS) through immunisation of adolescents and women of childbearing age.
• Achievement and maintenance of the required high vaccination coverage and high-quality surveillance of rubella and CRS, including laboratory testing of all suspected cases, are fundamental to eliminate rubella and prevent CRS in Europe.^[6]
• Checking rubella antibody status is part of antenatal care in the UK but this is too late for the current pregnancy.
• Checking rubella immunity should occur as part of preconception counselling.
• Elimination of both rubella and CRS should be possible via:
  • Universal immunisation of infants and young children.
  • Disease surveillance.
  • Ensuring immunity in women of childbearing age, prior to conception.
• Because the clinical diagnosis is so unreliable, a history of having had the disease is not a reason to forgo immunisation.
• Human normal immunoglobulin is not routinely used for post-exposure protection from rubella since there is no evidence that it is effective.
• Immunoglobulin is not recommended for the protection of pregnant women exposed to rubella. It should only be considered when termination of pregnancy is unacceptable.

Historical

• Sir Norman Gregg was an Australian ophthalmologist who first identified the link between maternal rubella in early pregnancy and congenital cataracts in infants in 1941.
• It was not until 1947 - when the Australian mathematician, Professor Oliver Lancaster, demonstrated the association statistically - that he was believed by the outside world.
• The rubella virus was isolated in 1961 and, following a worldwide outbreak in 1964-65 (20,000 cases of congenital cataract in the USA alone), vaccines were developed - the first being licensed in 1969: the shortest time period from virus identification to vaccine ever.
• The current RA 27/3 vaccine was introduced in 1979.