Rubella Virus

Indications for Testing

Prenatal screening for presence of maternal antibodies
Typical rash in unvaccinated patient

Criteria for Diagnosis

WHO case definition for congenital rubella syndrome

WHO Case Definition for Congenital Rubella Syndrome (CRS)

Suspected case
- Any infant <1 year in whom a health worker suspects CRS
  - A health worker should suspect CRS when an infant presents with heart disease and/or suspicion of deafness and/or one or more of the following eye signs: white pupil (cataract), diminished vision, pendular movement of the eyes (nystagmus), squint, smaller eye ball (microphthalmos), or larger eye ball (congenital glaucoma)
  - When an infant’s mother has a history of suspected or confirmed rubella during pregnancy, even when the infant shows no signs of CRS
Clinically confirmed case
- An infant in whom a qualified physician detects two of the complications in section A or one from section A and one from section B
  - Section A – cataracts, congenital glaucoma, congenital heart disease, hearing impairment, pigmentary retinopathy
  - Section B – purpura, splenomegaly, microcephaly, developmental delay, meningoencephalitis, radiolucent bone disease, jaundice with onset within 24 hours of birth
Laboratory-confirmed case
- An infant with rubella IgM antibody who has clinically confirmed CRS
Congenital rubella infection
- An infant with rubella IgM antibody who does not have clinically confirmed CRS

Laboratory Testing

Serology
- In primary rubella infection, the appearance of clinical symptoms is associated with the appearance of both IgG and IgM antibodies
  - IgM antibodies – detectable a few days after onset of symptoms; peak 7-10 days later
  - May consider fetal IgM serology if fetal infection suspected indicating previous infection and immunity
- Prenatal screening – test women prior to pregnancy to confirm presence of IgG antibodies indicating previous infection and immunity
PCR
- Usually throat or urine samples
- Amniotic fluid when fetus is at least 2 weeks of age to identify fetal infection

Differential Diagnosis

The reported number of rubella cases in the U.S. over the last 5 years is low enough for the Centers for Disease Control (CDC) to state that the endemic disease has been eliminated.

Epidemiology

Incidence – <25 cases a year in the U.S.
- Congenital rubella syndrome – <2/100,00 live births
Age – usually young children who are unvaccinated
Transmission
- Via droplets, aerosol particles – close contact required

Organism

Rubella, an RNA virus, is a member of the Togaviridae family
Virus infects cells in the upper respiratory tract and replicates in the lymphoid system; virus then spreads to other organs

Clinical Presentation

Transmission can occur up to 7 days before and 7 days after onset of the rash
In children and adults, infection usually results in mild, exanthematous disease
- Adults are more likely to experience prodromal phase – fever, headache, sore throat, cough, conjunctivitis
- Rare complications – arthralgias and arthritis, thrombocytopenia, hemorrhage and encephalitis
In pregnant women, particularly during first trimester, infection can result in fetal death or congenital abnormalities
- The spectrum of congenital defects called TORCH syndrome occurs with maternal exposure to rubella (also Toxoplasma gondii, cytomegalovirus and herpes simplex virus)
- Disease can be asymptomatic
  - Congenital abnormalities include the following
    - Eye defects – cataracts, glaucoma, iris hypoplasia, retinopathy
    - Sensorineural or central deafness
    - Congenital heart disease – patent ductus arteriosus, pulmonary stenosis, pulmonary arterial hypoplasias
    - Central nervous system – developmental delay with central nervous system calcifications, microcephaly
- 10-20% of newborns infected in utero will die during the first year of life
- Because complications in utero are so severe, diagnosis during first trimester may result in decision to terminate pregnancy
- Complications in survivors
  - Insulin-dependent diabetes mellitus
  - Rare panencephalitis
  - Thyroid dysfunction
  - Cataracts

Treatment

Treatment is supportive and symptom based

Prevention

Vaccination programs have resulted in marked decrease in infections
- Estimated >95% of children in U.S. are vaccinated (recommended between ages 12-15 months)
- Vaccine is live, attenuated virus and contraindicated in pregnant women

Tests generally appear in the order most useful for common clinical situations

Test name: Rubella Antibodies, IgG & IgM

ARUP #: 0050552

Methodology: Chemiluminescent Immunoassay

Use: Diagnose rubella infection

Follow-up: If test results are equivocal, repeat testing in 10-14 days

Test name: Rubella Antibody, IgG

ARUP #: 0050771

Methodology: Chemiluminescent Immunoassay

Use:

Determine immune status of females prior to pregnancy or for vaccination status

Additional Tests Available