important facts about the rubella virus?
1) Single-stranded positive sense RNA virus
2) family Matonaviridae in the genus Rubivirus
3) Glycosylated envelope proteins E1 and E2 - entry into cells
4) Neutralizing antibody responses are directed
against the E1 glycoprotein
Clinical presentation of Rubella virus?
- “3 day” measles
- Light pink erythematous maculopapular rash starts on face and spreads downwards lasting 1-3 days
- incubation period: 2- 3 weeks after inhalation of airborne droplets or direct contact with NP secretion from infected person
How long are people infectious before rash?
1 week before rash
How long are people infectious after rash?
2 weeks after rash
Rubella Sx in adults?
asymptomatic in 25-50% of cases
Low fever, sore throat, conjunctivitis, coryza, malaise 1-5 days before rash
Rubella sx in fetus?
1) Intrauterine Growth Restriction
2) Hepatosplenomegaly
3) Microcephaly
4) Hydrocephalus
5) Bony and cardiac abnormalities
Rubella sx in baby?
1) Jaundice
2) Blueberry rash
3) Hearing impairment in both sides
4) Cataracts
5) Chorioretinitis
6) Cardiac abnormalities
Laboratory diagnosis of rubella?
Which immunoglobulin is used before and during pregnancy and how?
which immunoglobulin is detected in infected babies and when?
1) IgM
- 5 -40 days post sx onset; second IgM screen should be done if negative at few days post sx onset
- Not recommended for screening asymptomatic individuals or pregnant women
- No fetal testing is recommended
- Baby tested after birth - IgM detection last up to 1 month post birth
2) IgG
*Before, during, and after birth
- Four-fold IgG titer between acute and convalescent serum (taken 1 week and 3 weeks
after symptom onset) -> acute infection - Testing for rubella IgG AVIDITY can be used to distinguish between recent exposure to
rubella and a more distant exposure
Avidity - stronger bond indicates Ab has seen Ag before so could indicate past infection
3) Nucleic Acid Detection by RT-PCR
- ACUTE INFECTION - NP SWAB
- 2 days before rash
- 4 days after rash
Diagnosis scenarios
If positive IgM but negative IgG, what does this mean and how to confirm?
Recent infection or false positive
Confirm:
1) RT-PCR of NP swab
2) another IgM (diff lab/technique)
3) collection of convalescent serum, 3-4 weeks to see IgG titer increase
Diagnosis scenarios
If positive IgM and IgG, what does this mean and how to confirm?
Recent infection or false positive with persistent IgM
Confirmation:
1) PCR
2) IgG avidity (IgG could be present since previous infection)
3) collection of another serum sample after 2 weeks to test for IgG changes
Treatment
- Supportive therapy: oral fluids, antipyretics, symptomatic control of the
rash and arthralgias/arthritis if present
What type of precautions should the patient be placed under?
droplet precautions cared
for only by individuals who are known to be immune to rubella virus
Vaccine?
- For children, two doses: MMR or MMRV
- 1st dose: 12 – 15 months
- 2nd dose: 4 – 6 years
- Older children, adolescents and adults: 1 or 2 doses of MMR if no evidence of immunity
Can get vaccine if exposed to measles, mumps, rubella - however vaccine within 72h will only protect against measles
