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.
• Transmission
  • Via droplets aerosol - close contact required

Organism

• Rubella, an RNA virus, is the only member of the Togaviridae family
• Virus infects cells in the upper respiratory tract and replicates in the lymphoid system
• Thereafter the virus 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 include 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 to Toxoplasma gondii, cytomegalovirus and herpes simplex virus)
  • Refer to Rubella topic at www.arupconsult.com for WHO case definitions for congenital rubella syndrome
    • Disease can be asymptomatic
    • Congenital abnormalities include:
      • Eye defects - cataracts, glaucoma, iris hypoplasia, retinopathy
      • Sensorineural or central deafness
      • Congenital heart disease (PDA, pulmonary stenosis, pulmonary arterial hypoplasias)
      • Central nervous system - mental retardation 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

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
  • Vaccine is live, attenuated virus and contraindicated in pregnant women

Diagnosis

• Indications for testing - prenatal screening for presence of maternal antibodies, rash in unvaccinated patient
• Laboratory testing
  • Antibody testing
    • 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
    • Prenatal screening - test women prior to pregnancy to confirm presence of IgG antibodies

Differential Diagnosis

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