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Congenital Rubella Syndrome Among the Amish -- Pennsylvania, 1991-1992

From February through May 1991, an outbreak of rubella occurred among the Amish in Pennsylvania that was part of a widespread rubella outbreak reported among the Amish in at least six states during 1991 (1). The Pennsylvania Department of Health (PDH), in cooperation with CDC, conducted an investigation to document cases of rubella among pregnant Amish women in Lancaster County and a cohort study to estimate the risk for congenital rubella syndrome (CRS) among infants born to Amish mothers from November 1, 1991, through January 31, 1992. This report summarizes investigation and study findings.

A case of maternal rubella was defined as the report of a rubella-like illness or serologic evidence of acute rubella infection during pregnancy. A case of CRS was defined as specified by the Council of State and Territorial Epidemiologists (2). Medical personnel involved in the obstetric care of Amish women obtained cord blood specimens for infants born of Amish mothers residing in Lancaster County (1990 total population: 422,822; Amish population 16,000-18,000) from November 1, 1991, through January 31, 1992; this period coincided with the expected delivery dates of most of the pregnant women who were in the first trimester of pregnancy during the rubella outbreak. In addition, the local family-practice residency program and a private obstetric practice obtained cord blood specimens from a systematic sample of non-Amish infants during the same period. The Pennsylvania Bureau of Laboratories tested all specimens for rubella-specific total (by latex agglutination) and IgM (by capture enzyme immunoassay) antibodies.

The PDH and CDC identified 89 Amish women from Lancaster and surrounding counties as having a rubella-like illness during pregnancy. Vaccination histories were available for 51 of these women, one of whom had a history of prior rubella vaccination. Of the 89 women, 18 (20%) had laboratory-confirmed acute rubella; for 31, specimens were insufficient for analysis (i.e., recent rubella infection could not be verified or excluded); and no specimens were obtained for the remaining 40. In addition to the 89, routine prenatal testing identified five Amish women who had serologic evidence of acute rubella, none of whom had experienced clinical illness.

The outcome of pregnancy was determined for the 94 Amish mothers who reported illness or had serologic evidence of maternal rubella (Table 1). CRS occurred in 10 infants, all of whom were born to mothers who had histories of rubella-like illness in the first trimester; seven had possible manifestations of CRS; nine were miscarried/stillborn; and 68 infants appeared normal at birth. During the study period, medical personnel identified one additional infant with CRS from Lancaster County whose mother was a conservative Mennonite.

Clinical abnormalities for the 11 infants with CRS included congenital heart disease (nine), deafness (six), purpura (four), long bone radiolucencies (four), cataracts (three), thrombocytopenia (three), hepatosplenomegaly (two), intracranial calcifications (two), encephalitis (one), microcephaly (one), failure to thrive (one), seizures (one), and disseminated intravascular coagulation (one).

For the cohort study, cord blood samples were collected from 103 infants born to Amish mothers (57% of the estimated 181 infants born to Amish mothers during the period) and 219 infants whose mothers were not Amish. Specimens for 15 (15%) of the 103 infants born to Amish mothers were positive for antirubella IgM antibody; in comparison, specimens from all 219 infants born to non-Amish mothers were negative. Seven (47%) of the 15 infants whose cord blood was positive by IgM were classified as having confirmed CRS, four (27%) had no clinical symptoms, and four (27%) had insufficient clinical information to allow classification. Based on the findings for the 3-month study period, the rate of congenital rubella infection was 83 per 1000 Amish live births and the rate of CRS was 40 per 1000 Amish live births. Reported by: R Anderson, MS, D Goslin, L Groff, MSN, M Howard, MSN, P Payne, PhD, R Rhoads-Martinez, D Abbott, DO, N Dragann, DO, J Rutt, MD, J Samitt, DO, DH Morton, MD, Clinic for Special Children; D Carr, Community Hospital of Lancaster; B Yingling, MD, RG Kimber, MD, Lancaster General Hospital; E Hershey, DR Tavris, MD, State Epidemiologist, Pennsylvania Dept of Health. Div of Immunization, National Center for Prevention Svcs; Div of Birth Defects and Developmental Disabilities, National Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: The risk for CRS is greatest when maternal infection occurs early in pregnancy; when infection occurs during the first trimester, CRS occurs in up to 85% of births (3). Manifestations of CRS range from mild to severe, with severely affected infants having multiple abnormalities, most notably cataracts, glaucoma, patent ductus arteriosus, pulmonary artery stenosis, meningoencephalitis, microcephaly, and mental retardation. Preventing fetal infection and the serious consequences of CRS is the goal of rubella vaccination efforts (4). Rubella vaccination strategies to prevent CRS include 1) identification and vaccination of nonimmune women of childbearing age and 2) routine vaccination of all children aged greater than or equal to 15 months to decrease circulation of wild virus.

In 1988, 225 cases of postnatal rubella were reported from 23 states and Puerto Rico -- the lowest number ever reported in the United States. During 1989-1991, the number of reported cases of postnatal rubella and the number of states reporting cases increased each year; these increases have reflected, in part, large outbreaks that occurred during 1990-1991 in California and among the Amish and Mennonites in six states (1,5).

For CRS, an annual average of two cases were reported per year from 1984 to 1989 (excluding an outbreak of eight cases in New York City during 1986). However, in 1990 and 1991, reported CRS increased markedly as did the total number of states reporting CRS cases (Figure 1). During 1986-1991, 68 cases of indigenous, confirmed, or compatible CRS (1) were reported to CDC's National CRS Registry. Most (49) of these were associated with three known outbreaks of CRS: New York City during 1986 (eight cases), California during 1990-91 (25 cases), and among the Amish in Pennsylvania and New York in 1991 (16 cases). However, 19 (28%) cases were reported from 11 states that did not report large rubella outbreaks during this period. These cases most likely represent inadequate diagnosis and reporting of rubella despite circulation of rubella virus. Of the 68 mothers entered in the National CRS Registry for 1986-1991, 36 (53%) had prior live-born infants; however, only six (17%) reported rubella vaccination, and only four of those without history of vaccination were reported to be immune. Overall, 26 (38%) of these mothers had prior pregnancies but were either not tested or not vaccinated for rubella as recommended by the Advisory Committee for Immunization Practices (4).

The increased occurrence of rubella and CRS in the United States underscores the need for heightened awareness among physicians and other health-care providers in diagnosing rubella and CRS. Suspected rubella cases should be promptly reported to local health departments to facilitate early detection of outbreaks and implementation of control measures. In addition, efforts to vaccinate children and women of childbearing age must be intensified (4). Postpartum vaccination of susceptible women could have prevented up to 38% of the CRS cases reported during 1986-1991. To prevent CRS, women of childbearing age who are not pregnant should be evaluated for rubella immunity (i.e., documented history of rubella vaccination or serologic evidence of rubella immunity) during any health-care visit (e.g., visits following spontaneous or therapeutic abortions, family planning, sexually transmitted disease treatment, and routine gynecologic care) and, if indicated, vaccinated.

The PDH has used these findings 1) in their efforts to promote vaccination among the state's Amish population, including publishing articles on rubella vaccination in local Amish newsletters, and 2) in encouraging state health-care providers to intensify vaccination efforts among groups who traditionally refuse vaccination.


  1. CDC. Outbreaks of rubella among the Amish -- United States, 1991. MMWR 1991;40:264-5.

  2. CDC. Case definitions for public health surveillance. MMWR 1990;39(no. RR-13):32.

  3. Miller E, Cradock-Watson JE, Pollock TM. Consequences of confirmed maternal rubella at successive stages of pregnancy. Lancet 1982;2:781-5.

  4. ACIP. Rubella prevention: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1990;39(no. RR-15):1,10-2.

  5. Lindegren ML, Fehrs LJ, Hadler SC, Hinman AR. Update: rubella and congenital rubella syndrome, 1989-1990. Epidemiol Rev 1991;13:341-8.

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