Rubella Virus

Diagnosis

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

• CDC - testing recommendations
• 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

• Measles virus
• Parvovirus B19
• Human herpesvirus 6 (HHV6)
• West Nile virus
• Enterovirus
• Dengue fever virus

Clinical Background

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 – <2/100,000 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

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Rubella Antibody, IgM 0050551 Method: Chemiluminescent Immunoassay
TORCH Antibodies, IgG 0050772 Method: Chemiluminescent Immunoassay
TORCH Antibodies, IgM 0050665 Method: Semi-Quantitative Chemiluminescent Immunoassay/Semi-Quantitative Enzyme-Linked Immunosorbent Assay