Rubella Virus

 Key Points to Remember

·        Rubella virus is an enveloped, single-stranded RNA virus from the Togaviridae family that causes German measles.

·        It spreads through respiratory droplets and can also cross the placenta, infecting the fetus.

·        Infection in early pregnancy can cause Congenital Rubella Syndrome (CRS) with severe birth defects.

·        There is no specific treatment; management is mainly supportive.

·        Prevention through MMR vaccination is the most effective way to control and eliminate rubella.

Keywords

Rubella virus, German measles, Congenital Rubella Syndrome, Rubella in pregnancy, MMR vaccine.

Rubella Virus

Introduction

Rubella, commonly known as German measles, is a contagious viral infection caused by the Rubella virus, a member of the Togaviridae family and Rubivirus genus. Although rubella is generally mild in children and adults, infection during pregnancy can cause severe fetal abnormalities, making it a major concern in public health and prenatal care.

Characteristics of Rubella Virus

• Family: Togaviridae
• Genus: Rubivirus
• Genome: Single-stranded, positive-sense RNA
• Shape: Spherical, enveloped virus (≈60 nm in diameter)
• Capsid: Icosahedral symmetry
• Surface proteins: E1 and E2 glycoproteins that help in attachment and entry into host cells

The virus is sensitive to heat, ultraviolet radiation, and detergents, and it replicates primarily in the cells of the respiratory tract.

Replication Cycle

1.     Attachment and Entry: The virus binds to host cell receptors via its E1 glycoprotein and enters through receptor-mediated endocytosis.

2.     Uncoating: The viral envelope fuses with the endosomal membrane, releasing RNA into the cytoplasm.

3.     Translation: Viral RNA acts directly as mRNA, producing non-structural proteins.

4.     Replication: The virus synthesizes a negative RNA strand that serves as a template for new positive strands.

5.     Assembly: New virions assemble in the cytoplasm.

6.     Release: The virus buds from the host cell, acquiring its envelope.

Transmission

Rubella spreads mainly through:

• Respiratory droplets from coughs or sneezes
• Direct contact with infected nasopharyngeal secretions
• Transplacental transmission from mother to fetus

An infected person can transmit the virus 7 days before to 7 days after the rash appears.

Epidemiology

Before vaccination programs, rubella occurred worldwide in epidemics every 6–9 years. After the introduction of the MMR (Measles-Mumps-Rubella) vaccine, the disease became rare in most developed countries. However, rubella remains endemic in regions with low immunization coverage, including parts of Asia and Africa.

Pathogenesis

1.     Entry and replication: The virus enters via the respiratory tract and replicates in nasopharyngeal and lymphoid tissues.

2.     Viremia: It spreads through the bloodstream to multiple organs.

3.     Rash formation: Immune complexes between rubella antigens and antibodies deposit in the skin, causing the characteristic maculopapular rash.

4.     Placental infection (in pregnancy): The virus crosses the placenta, infecting the fetus and disrupting organ development.

Immunity

• Infection induces lifelong immunity through neutralizing antibodies.
• Maternal antibodies protect infants for 6–9 months after birth.
• Vaccination with the live attenuated rubella vaccine also provides long-term protection.

Symptoms

Rubella symptoms usually appear 14–21 days after exposure and may include:

• Mild fever
• Headache
• Sore throat
• Swollen lymph nodes (especially behind the ears)
• Fine, pink, maculopapular rash starting on the face and spreading downward
• Joint pain (more common in adults, especially females)

Up to 50% of infections can be asymptomatic, contributing to unnoticed transmission.

Congenital Rubella Syndrome (CRS)

When a pregnant woman contracts rubella during the first trimester, the virus can cause Congenital Rubella Syndrome, leading to:

• Deafness
• Cataracts
• Heart defects (e.g., patent ductus arteriosus)
• Growth retardation
• Mental retardation
• Hepatosplenomegaly and thrombocytopenia

The risk of fetal infection is highest during the first 12 weeks of gestation.

Diagnosis

1.     Serological tests: Detection of rubella-specific IgM and IgG antibodies.

2.     PCR (Polymerase Chain Reaction): Detects viral RNA in blood or throat swabs.

3.     Prenatal diagnosis: In suspected maternal infection, amniocentesis can be used to detect viral RNA in amniotic fluid.

Rubella in Pregnant Women

Infection during early pregnancy poses serious risk to the fetus:

• Women infected within first 12 weeks → up to 85% chance of CRS.
• Between 13–16 weeks → 35% risk.
• After 20 weeks, fetal risk is minimal.

Pregnant women should not receive the live vaccine but should be vaccinated before conception.

Treatment

There is no specific antiviral therapy for rubella.
Treatment focuses on:

• Rest and hydration
• Fever control with acetaminophen or paracetamol
• Isolation to prevent spread
• Symptomatic relief for rash and joint pain

In congenital cases, supportive care and early detection of complications are essential.

Prevention

1.     Vaccination:

o    MMR Vaccine (Measles, Mumps, Rubella) is given in two doses:

§  1st dose at 12–15 months

§  2nd dose at 4–6 years

o    Provides >95% protection.

2.     Prenatal screening: Check rubella immunity in women before pregnancy.

3.     Herd immunity: Maintaining >90% vaccination coverage prevents outbreaks.

4.     Infection control: Isolate infected individuals for at least one week after rash onset.

Conclusion

Rubella is a preventable viral disease that remains a significant concern for maternal and child health. Widespread immunization and awareness are key to eradicating rubella and preventing congenital rubella syndrome. Early vaccination, proper diagnosis, and public education are the cornerstones of rubella control worldwide.