Structure & Property

Transmission

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment

Family: togavirus

Genome: single-strand RNA, negative polarity

Size: 50-75nm

Icosahedral nucleocapsid

Pleomorphic, enveloped particles: surface spikes contain hemagglutinin.

Single serotype.

Antibody against hemagglutinin neutralizes infectivity.

Rapidly inactivated at 56 degrees.

No virion polymerase.

RNA translate into structural & non-structural proteins.

Transmitted via respiratory droplets.

Present in both blood and pharyngeal secretions.

Humans are natural host.

Natural infection leads to lifelong immunity.

Children in utero continue to excrete rubella for months following birth.

Some congenital shedders are asymptomatic and without malformations.

Initial replication in nasopharynx and local lymph nodes.

Spreads via blood to internal organs and skin.

Antibodies cross placenta & protects newborn.

Incubation period: 14-21 days

Brief prodromal period:

- fever

- malaise

- maculopapular rash that starts on face and progresses to extremities.

Rash typically lasts for 3 days.

Posterior auricular lymphadenopathy.

Polyarthritis common in adult women.

Rubella is a mild disease, but if contracted in early pregnancy the virus can cause severe congenital abnormalities and disease in fetus.

Congenital defects occur if mother has rubella in the first 16 weeks of pregnancy; after than rubella does not damage the fetus.

Congenital rubella syndrome:

- eye: cataracts

- heart: patent ductus arteriosus

- CNS: deafness & mental retardation.

Rare, late complication: SSPE

Use of diagnosis:

- confirm suspected rubella in a pregnant woman.

- detect non-immune pregnant women.

Serology:

- IgM antibody by ELISA or immunofluorescence: recent infection.

- single radial haemolysis.

Diagnosis can be made by observing 4-fold rise in antibody titer between acute phase and convalescence.

Amniocentesis can reveal whether there is rubella virus in amniotic fluid.

PCR used to detect rubella virus RNA

Haemagglutinates avian erythrocytes.

Inhibit echovirus CPE

Grows in rabbit tissue cell line with CPE; no CPE in other tissue cultures.

Single radial hemolysis:

- detect immunity in pregnant women or women at risk.

- does not measure antibody titre.

No antiviral treatment is available.

Prevention involves immunization with live, attenuated vaccine.

Vaccine cause a marked decrease in incidence of both rubella and congenital rubella syndrome.

Vaccine induces IgA and impairs spread of virus.

Administration of immune globulin dose not prevent fetal infection in pregnant women exposed to the virus.