Measles, Mumps, and Rubella - Centers for Disease Control and ...

4 MMWR May 22, 1998b) ensuring that all school-aged children receive a second dose of MMR vaccine, andc) working with other countries to set and achieve national measles elimination goals.Rubella And Congenital Rubella Syndrome (CRS)Clinical CharacteristicsRubella is an exanthematous illness characterized by nonspecific signs and symptomsincluding transient erythematous and sometimes pruritic rash, postauricular orsuboccipital lymphadenopathy, arthralgia, and low-grade fever. Clinically similar exanthematousillnesses are caused by parvovirus, adenoviruses, and enteroviruses.Moreover, 25%–50% of rubella infections are subclinical. The incubation period rangesfrom 12 to 23 days. Before rubella vaccine was available, the disease was commonamong children and young adults.Among adults infected with rubella, transient polyarthralgia or polyarthritis occurfrequently. These manifestations are particularly common among women (18 ). Centralnervous system complications (i.e., encephalitis) occur at a ratio of 1 per 6,000cases and are more likely to affect adults. Thrombocytopenia occurs at a ratio of 1 per3,000 cases and is more likely to affect children.The most important consequences of rubella are the miscarriages, stillbirths, fetalanomalies, and therapeutic abortions that result when rubella infection occurs duringearly pregnancy, especially during the first trimester. An estimated 20,000 cases ofCRS occurred during 1964–1965 during the last U.S. rubella epidemic before rubellavaccine became available.The anomalies most commonly associated with CRS are auditory (e.g., sensorineuraldeafness), ophthalmic (e.g., cataracts, microphthalmia, glaucoma, chorioretinitis),cardiac (e.g., patent ductus arteriosus, peripheral pulmonary artery stenosis, atrial orventricular septal defects), and neurologic (e.g., microcephaly, meningoencephalitis,mental retardation). In addition, infants with CRS frequently exhibit both intrauterineand postnatal growth retardation. Other conditions sometimes observed among patientswho have CRS include radiolucent bone defects, hepatosplenomegaly,thrombocytopenia, and purpuric skin lesions.Infants who are moderately or severely affected by CRS are readily recognizable atbirth, but mild CRS (e.g., slight cardiac involvement or deafness) may be detectedmonths or years after birth, or not at all. Although CRS has been estimated to occuramong 20%–25% of infants born to women who acquire rubella during the first20 weeks of pregnancy, this figure may underestimate the risk for fetal infection andbirth defects. When infants born to mothers who were infected during the first8 weeks of gestation were followed for 4 years, 85% were found to be affected (19 ).The risk for any defect decreases to approximately 52% for infections that occur duringthe ninth to twelfth weeks of gestation. Infection after the twentieth week ofgestation rarely causes defects. Inapparent (subclinical) maternal rubella infection canalso cause congenital malformations. Fetal infection without clinical signs of CRS canoccur during any stage of pregnancy.