Rubella( German measles )

Etiology Togaviridae family --- genus Rubivirus single-stranded RNA enveloped virus , Its core protein is surrounded by a single-layer lipoprotein envelope with spike-like projections containing two glycoproteins, E1 and E2. only one antigenic type humans are its only known reservoir

Pathogenesis and Pathology Transmission: respiratory droplets. Primary implantation and replication in the nasopharynx are followed by spread to the lymph nodes. Subsequent viremia occurs, which in pregnant women often results in infection of the placenta. Placental virus replication may lead to infection of fetal organs. Individuals with acquired rubella may shed virus from 7 days before rash onset to 5–7 days Infants with CRS may shed large quantities of virus from bodily secretions, particularly from the throat and in the urine, up to 1 year of age. Outbreaks of rubella, including some in nosocomial settings, have originated with index cases of CRS. Thus only individuals immune to rubella should have contact with infants who have CRS

Clinical Features: Acquired Rubella Up to 50% subclinical or inapparent. Young chid: generalized maculopapular rash that usually lasts for up to 3 days . The rash is usually mild and may be difficult to detect in persons with darker skin older children and adults: The incubation period is 14 days (range, 12–23 days), 1- to 5-day prodrome often precedes the rash and may include low-grade fever, malaise, and upper respiratory symptoms. Lymphadenopathy, particularly occipital and postauricular, may be noted during the second week after exposure. arthralgia and arthritis are common in infected adults, particularly women Thrombocytopenia and encephalitis are less common complications.

Congenital Rubella Syndrome infected during pregnancy(first trimester): miscarriage, fetal death, premature delivery, or live birth with congenital defects. commonly relate to the eyes, ears, and heart Transient Manifestation: Hepatosplenomegaly , Interstitial pneumonitis, Thrombocytopenia with purpura/petechiae (e.g., dermal erythropoiesis, or "blueberry muffin syndrome"), Hemolytic anemia, Bony radiolucencies, Intrauterine growth retardation, Adenopathy  , Meningoencephalitis Permanent Manifestations: Hearing impairment/deafness, Congenital heart defects (patent ductus arteriosus, pulmonary arterial stenosis), Eye defects (cataracts, cloudy cornea, microphthalmos, pigmentary retinopathy, congenital glaucoma), Microcephaly, Central nervous system sequelae (mental and motor delay, autism)

Diagnosis: acquired scarle fever, roseola, toxoplasmosis, fifth disease, measles, and illnesses with suboccipital and postauricular lymphadenopathy Laboratory : Serology: acute: 1- IgM antibodies 2- fourfold rise in IgG antibody titer between acute- and convalescent-phase specimens. 3- IgG avidity testing is used in conjunction with IgG testing. Low- avidity antibodies indicate recent infection. Mature (high-avidity) IgG antibodies most likely indicate an infection occurring at least 2 months previously. Rubella virus can be isolated from the blood and nasopharynx during the prodromal period and for as long as 2 weeks after rash onset. However, as the secretion of virus in individuals with acquired rubella is maximal just before or up to 4 days after rash onset, this is the optimal time frame for collecting specimens for viral cultures. Rubella RNA detection by reverse-transcriptase polymerase chain reaction (RT- PCR) is a more recently developed technique for rubella diagnosis.

Congenital Rubella Syndrome infant presents with a combination of cataracts, hearing impairment, and heart defects serologic assays: serum IgM antibodies may be present for up to 1 year after birth. In some instances, IgM may not be detectable until 1 month of age rubella serum IgG titer persisting beyond the time expected after passive transfer of maternal IgG antibody (i.e., a rubella titer that does not decline at the expected rate of a twofold dilution per month) virus isolated: throat swabs and less commonly from urine and cerebrospinal fluid. Infants with congenital rubella may excrete virus for up to 1 year, but specimens for virus isolation are most likely to be positive if obtained within the first 6 months after birth. Rubella virus in infants with CRS can also be detected by RT-PCR.

Pregnant women screening for rubella IgG antibodies in prenatal care positive IgG antibody serologic test are considered immune. Susceptible pregnant women should be vaccinated postpartum A susceptible pregnant woman exposed to rubella virus should be tested for IgM antibodies and a fourfold rise in IgG antibody titer between acute- and convalescent-phase serum specimens : during the first 11 weeks of gestation, up to 90% deliver an infant with CRS; for maternal infection during the first 20 weeks of pregnancy, the CRS rate is 20%.

Treatment No specific therapy Symptom-based treatment Immunoglobulin does not prevent rubella virus infection only in pregnant woman who has been exposed to rubella will not consider termination of pregnancy under any circumstances( IM administration of 20 mL of immunoglobulin within 72 h of rubella exposure)

Prevention Rubella vaccine contains live attenuated rubella virus grown in human diploid cells (RA 27/3). combined with measles and rubella (MR) or measles, mumps, and rubella (MMR) formulations, tetravalent measles, mumps, rubella, and varicella (MMRV) vaccine. One dose induces seroconversion in 95% of persons >1 year of age. rubella vaccination in the United States is a first dose of MMR vaccine at 12–15 months of age and a second dose at 4–6 years. Indication: children >1 year of age, adolescents and adults without documented evidence of immunity, individuals in congregate settings (e.g., college students, military personnel, child care and health care workers), and susceptible women before and after pregnancy. women known to be pregnant should not receive an RCV. In addition, pregnancy should be avoided for 28 days after receipt of an RCV. In follow-up studies of 680 unknowingly pregnant women who received rubella vaccine, no infant was born with CRS. Receipt of an RCV during pregnancy is not ordinarily a reason to consider termination of the pregnancy.