Microbiology · MU Sofia

93. Rubella Virus & Zika Virus

Covers rubella and Zika viruses side by side, starting with rubella's general features, transmission and pathogenesis, then its clinical picture with the congenital rubella syndrome triad, diagnosis and prevention. The Zika section follows the same order, covering mosquito and other routes, fetal effects, diagnostic cautions and vector control. A closing table compares the two viruses on family, transmission, congenital syndrome, rash, diagnosis and vaccine.

Inside: 3 sections · 9 labelled pictures · 2 tables · 13 flashcards · 4 min

Topic 93 of 113 in the MU Sofia syllabus for Microbiology (Medicine, Year 3). The free AceMed note covers it in 3 sections, about 510 words (4 min of reading), with 13 flashcards.

In this note

  1. Rubella Virus & Zika Virus
  2. Rubella Virus
  3. Zika Virus

Rubella Virus

I. General Features

  • Enveloped, positive-sense single-stranded RNA virus (+ssRNA).
  • Icosahedral nucleocapsid; replicates in the cytoplasm.
  • Human is the only reservoir.
  • Transmission is via respiratory droplets and transplacental (vertical) during pregnancy.
  • Mild exanthematous infection in children, but teratogenic in fetus → Congenital Rubella Syndrome (CRS).

II. Pathogenesis

  • Virus enters via nasopharyngeal mucosa, replicates in local lymphoid tissue.
  • Viremia develops within 5–7 days → spreads systemically.
  • Infection during first trimester of pregnancy → virus crosses placenta → replicates in fetal tissues.
  • Damage is due to interference with mitosis, cell necrosis, and vascular injury in developing organs.

III. Virulence Factors

  • E1 glycoprotein: mediates viral attachment and fusion.
  • Transplacental transmission capability → pathogenesis of CRS.
  • Induces immune complex deposition → contributes to rash.

IV. Clinical Features

  • Incubation: 14–21 days.
  • In children/adults:
  • Low-grade fever
  • Maculopapular rash starting on face → trunk and limbs
  • Postauricular, occipital lymphadenopathy (KEY FINDING)
  • Arthralgia/arthritis (especially in females)
  • Congenital Rubella Syndrome (CRS):
  • Highest risk if infection occurs in 1st trimester
  • Classic Triad:
  1. 1. Cataracts
  2. 2. Deafness (sensorineural)
  3. 3. Congenital heart defect (PDA most common)
  • Other features:
  • Microcephaly
  • Hepatosplenomegaly
  • “Blueberry muffin” rash (due to extramedullary hematopoiesis)

V. Diagnosis

  • Rubella-specific IgM (ELISA or CLIA)
  • Fourfold rise in IgG titers in paired sera
  • RT-PCR for confirmation (especially in CRS cases)

VI. Prevention & Treatment

  • No antiviral therapy; only symptomatic treatment.
  • Live attenuated MMR vaccine (contraindicated in pregnancy).
  • 1st dose at 12–15 months, 2nd at 4–6 years.
  • Screening pregnant women for rubella immunity (IgG).
  • Infected pregnant woman → high risk of fetal damage → possible counseling for pregnancy termination in early infection.

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