Rubella Infection

Group 3

Rubella Virus

• From Latin meaning “little red”

• Acquired rubella; German measles; 3-day measles

• Caused by an enveloped, single stranded RNA virus of the Togaviridae family

• Highly contagious and transmitted through respiratory secretions

• Occurred most often in childhood

Rubella Pathogenesis

• Respiratory transmission of virus

• Replication in nasopharynxand regional lymph nodes

• Viremia 5-7 days after exposure with spread to tissues

• Placenta and fetus infected during viremia

Individuals requiring rubella immune status determination:

• Preschool-age and school-age children

• All females at or just before childbearing age

• Women about to be married

• Married woman

• Pregnant woman

• Health care personnel

Clinical Features

• Incubation period 14 days (range 12-23 days)

• Prodrome of low grade fever

• Lymphadenopathy in second week

• Maculopapular rash 14-17 days after exposure

• Koplik spots are

seen with measles.

They are small, white

spots (often on an

reddened background)

that occur on the inside

of the cheeks early in

the course of measles

may appear as irregular

red spots with a minute,

bluish white center

opposite molars 2 days

before rash

Congenital Rubella Syndrome

• Infection may affect all organs

• May lead to fetal death or premature delivery

• Severity of damage to fetus depends on gestational age

• Up to 85% of infants affected if infected during first trimester

Fetal abnormalities associated with maternal rubella infection:

• Encephalitis; • Hepatomegaly; • Bone defects; • Mental retardation; • Cataracts ; • Thrombocytopenic

purpura; • Cardiovascular defects; • Splenomegaly; • Microcephaly

Immunologic Manifestations:

Diagnostic evaluation

1. Hemagglutination Inhibition (HAI)• Most frequently used method of screening for the presence of

rubella; reference method

• Disadvantage: it can detect a combination of IgM and IgGantibodies but it does not distinguish between them

2. Enzyme immunoassay for Antibodies• The rubella-specific IgM often persists for 20 to 30 days after

acute infection or vaccination and also in infants with congenital rubella

3. Latex agglutination• Provide more rapid and convenient alternatives for HAI

• Positive result: visible clumps

• Negative result: latex particles are remain smooth and evenly dispersed

• Single specimen are required for qualitative determination of antibody levels

• Two specimens for quantitative testing

• The first specimen should be collected within 3 days of the onset of rash or at the time of exposure and tested on arrival in the laboratory

• 2nd specimen is collected 7 to 21 days after the onset of tha rash or at least 30 days after exposure if no clinical symptoms occur.

• 2 ml of blood collected in red top evacuated tube

• Specimens maybe stored up to 48 hours at 2-8 degree C

• Sodium azide preservative present in latex reagent, buffer and control

• 4. Flourescent immunoassay

• Qualitative test card

– Used to detect the presence of rubella antibody