Current Trends Increase in Rubella and Congenital Rubella Syndrome -- United States, 1988-1990

In 1988, health departments in the United States reported an all-time low of 225 cases of rubella. However, in 1989, the number of reported cases increased nearly twofold, and in 1990, an additional threefold. As of January 4, 1991, a provisional total of 1093 cases (0.4 cases per 100,000 population) had been reported to the National Notifiable Disease Surveillance System (NNDSS) for 1990--the highest total since 1982 (Figure 1). This report summarizes the increase in rubella and congenital rubella syndrome (CRS) since 1988. Rubella

In 1990, provisional rubella reports were received from 38 states and the District of Columbia, compared with 29 states and Puerto Rico in 1989 and 23 states and Puerto Rico in 1988 (Figure 2).* From 1988 through 1990, the incidence of rubella increased primarily in the West and Midwest. California, which reported half of U.S. cases in 1990, reported a nearly fourfold increase in reports from 1989 to 1990. Rubella outbreaks in Amish communities during 1990 resulted in a substantial increase in case reports from Minnesota, New York, and Ohio.

For all states except California, age-specific data on rubella case-patients are available in NNDSS for 1988 and 1989 (Table 1); data for 1990 are provisional. When compared with 1988, the largest age-specific increases in rubella incidence in 1989 occurred among persons aged greater than or equal to 15 years and among infants aged less than 1 year. When compared with 1989, a greater proportion of cases in 1990 occurred among persons aged 1-14 years (Table 1), reflecting the contribution of outbreaks in religious communities that involved substantial numbers of cases among unvaccinated children. A CDC and local investigation in California determined that 325 (81%) of 400 cases reported with patient age from January through June 7, 1990, occurred among persons aged greater than or equal to 15 years. Based on these findings and on NNDSS reports in 1990, the incidence rate of rubella in the United States from 1988 to 1990 increased most for persons aged 15-29 years (from 0.1 to 0.6 per 100,000 persons) and for persons aged greater than or equal to 30 years (from 0.02 to 0.2 per 100,000).

Distinct outbreaks of rubella cannot be identified from data in NNDSS. Based on other information provided to CDC's Center for Prevention Services, 26 rubella outbreaks in 1990 could be distinguished and classified into two categories:

1. Outbreaks in which all cases occurred in or were linked to settings in which unvaccinated adults congregate (e.g., prisons, colleges, and workplaces). Ten outbreaks (nine from California and one from Michigan) occurred in prisons and involved from three to an estimated 36 persons. Four outbreaks (in California, Idaho, Montana, and New York) occurred in colleges and involved from six to an estimated 18 or more persons. Outbreaks among adults were also reported in the workplace and in community and recreational settings.

2. Outbreaks among children and adults in religious communities with low levels of rubella vaccination coverage. The three reported outbreaks in Amish communities included from nine to 128 reported cases. An outbreak involving at least 69 persons occurred in a different religious community in Oregon.

Data on vaccination status of rubella patients are not collected in NNDSS; however, the investigation in California obtained information on vaccination status on 61 (74%) of 82 patients identified in one county outbreak. For 53 (87%) of the 61 patients, no specific history of rubella vaccination was reported. Data obtained on 26 outbreaks reported to CDC in 1990 also indicate that vaccinated persons accounted for a relatively small number of rubella cases. Congenital Rubella Syndrome

For 1990, 10 confirmed** cases of CRS among infants born in the United States have been reported to CDC's National Congenital Rubella Syndrome Registry (NCRSR); laboratory confirmation is pending for an additional case compatible with CRS (Table 2).*** As of January 4, 1991, CDC received five additional provisional reports of confirmed or compatible indigenous CRS cases. In contrast, during 1988 and 1989, two infants and one infant with CRS were born, respectively. In addition, a provisional total of three imported cases of CRS p has been reported for 1990.

Nine of the 11 CRS case-patients born in 1990 were born in southern California--five in Los Angeles County, two in Orange County, one in San Diego County, and one in Ventura County. The five provisional case-patients were born in Los Angeles County. In early 1990, a large outbreak of rubella occurred in Orange County; in the other three counties, reported rubella incidence increased less markedly or was unchanged. The other CRS cases were reported in Iowa and Montana.

Of the 11 mothers of the case-patients reported to NCRSR, five were white, five were Hispanic, and one was black; their median age was 23 years (range: 18-31 years). Although two women provided a specific history of rubella vaccination, these histories were not confirmed. One of these two mothers was reported to have had a positive test for rubella antibody before pregnancy; however, no serum specimens were available to assess prior immunity. An epidemiologic investigation is ongoing to further characterize the mothers of CRS case-patients and to identify missed opportunities for preventing rubella infection in these women. Reported by: L Mascola, MD, Acute Communicable Disease Control, SL Fannin, MD, Disease Control Programs, County of Los Angeles, Dept of Health Svcs; D Chitty, Orange County Health Dept; W Forney, MD, Stanislaus County Health Dept; LG Dales, MD, Immunization Unit, GW Rutherford, III, MD, State Epidemiologist, California Dept of Health Svcs. HP Osterud, MD, Clackamas County Public Health Div; BJ Fineout, MPH, DW Fleming, MD, Oregon State Health Div, Dept of Human Resources. Surveillance, Investigations, and Research Br, Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Reports from health departments in 1990 indicate a moderate resurgence of rubella and a major increase in CRS in the United States. This resurgence followed a substantial reduction in reported rubella cases during the 1980s, which was associated with an increased emphasis on vaccinating adolescents and adults, particularly women of childbearing age. From 1966 through 1987, rubella incidence decreased 96% in persons greater than or equal to 20 years of age (2). However, because a substantial proportion (6%-25% (3)) of women of childbearing age remained susceptible, the potential risk for CRS persisted.

Many of the rubella outbreaks in 1990 occurred in settings in which adolescents and adults congregate and transmission to susceptible persons can occur. In California, at least 14 pregnant women were exposed to rubella as a result of prison or jail exposure.

For at least four reasons, the investigation of rubella in California suggested a true increase in rubella incidence in 1990, rather than an increase in diagnosis and reporting of rash illnesses because of widespread measles outbreaks. First, the age, race, and geographic distributions of rubella patients differed substantially from those of measles patients. Second, in 1990, rubella outbreaks occurred in nine state prisons or county jails, compared with one and three such outbreaks in 1988 and 1989, respectively. Third, the number of specimens submitted to the state laboratory for diagnostic rubella testing and the proportion that tested positive increased substantially from 1989 to 1990. Finally, the cluster of CRS cases occurred in southern California.

Despite the increased incidence of rubella in 1990, the rate for 1990 still represented a decline of 98% from that for 1966-1968 (24.3 per 100,000 population), the period immediately before vaccine licensure. Limited data from outbreaks reported in 1990 suggest that failure to vaccinate, rather than vaccine failure, has been responsible for the increase in rubella. This conclusion is supported by studies showing the long-term persistence of vaccine-induced immunity to rubella (4).

The goal of rubella vaccination is to prevent intrauterine rubella infection, which can result in miscarriage, stillbirth, or CRS or consideration of termination of pregnancy. In 1983, the average lifetime expenditure associated with providing care for an infant with CRS was estimated to exceed $200,000 (5). The increase in CRS cases reported in 1990 indicates a need to improve vaccination levels among adults, especially among women of childbearing age.

Several strategies may be necessary to improve rubella prevention and control and to better understand the epidemiology of rubella in the United States: 1) encouraging strong efforts by health-care providers and public health officials to implement the recommendations of the Immunization Practices Advisory Committee to improve rubella vaccine coverage levels among children and adults, particularly women of childbearing age (6); 2) establishing prevention and control programs in all correctional facilities; 3) initiating prompt and aggressive control measures whenever rubella outbreaks are reported; 4) increasing attention to the diagnosis and surveillance of rubella and CRS (e.g., in 21 states, the public health laboratory actively seeks rubella cases by performing rubella serologic testing on all specimens submitted for measles diagnosis that test negative for measles antibody); and 5) using population-based serologic surveys, rubella outbreak investigations, and special studies to determine the prevalence of rubella susceptibility, populations at risk, risk factors for nonvaccination, and missed or underused opportunities to vaccinate susceptible adults and adolescents. Because CRS is the most severe and preventable consequence of rubella infection, CRS cases should be identified and investigated to estimate incidence and identify opportunities to prevent rubella infection in mothers (7,8).

References

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

2. CDC. Rubella and congenital rubella syndrome--United States, 1985-1988. MMWR 1989;38:173-8.

3. Stehr-Green PA, Cochi SL, Preblud SR, Orenstein WA. Evidence against increasing rubella seronegativity among adolescent girls. Am J Public Health 1990;80:88.

4. Chu SY, Bernier RH, Stewart JA, et al. Rubella antibody persistence after immunization: sixteen-year follow-up in the Hawaiian Islands. JAMA 1988;259:3133-5.

5. White CC, Koplan JP, Orenstein WA. Benefits, risks, and costs of immunization for measles, mumps, and rubella. Am J Public Health 1985;75:739-44.

6. CDC. Rubella prevention: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1990;39(no. RR-15).

7. Cochi SL, Edmonds LD, Dyer K. Congenital rubella syndrome in the United States, 1970-1985: on the verge of elimination. Am J Epidemiol 1989;129:349-61.

8. Kaplan KM, Cochi SL, Edmonds LD, Zell ER, Preblud SR. A profile of mothers giving birth to infants with congenital rubella syndrome: an assessment of risk factors. Am J Dis Child 1990;144:118-22.

• Mississippi does not require reporting of rubella cases. ** Based on definitions recommended by the Council of State and Territorial Epidemiologists (CSTE), a confirmed CRS case is a case with both congenital anomalies and laboratory evidence of rubella infection in a person, and a compatible case is a case that satisfies selected clinical criteria without laboratory confirmation (1).

*** Data on CRS are available from reports submitted weekly to NNDSS and from NCRSR maintained at CDC's Center for Prevention Services. The NNDSS CRS reports are case counts with demographic data and are tabulated by year of report. The NCRSR contains clinical and laboratory information on cases of CRS that are reported by state and local health departments. NCRSR cases are classified by year of patient's birth; data are considered provisional for any given year, because delays in diagnosis or reporting may result in updates of these figures.

p Based on definitions approved by CSTE, an imported case of CRS is defined as CRS in a U.S. or non-U.S. citizen whose mother was outside the United States during her presumed exposure to rubella. If the timing of exposure to rubella cannot be determined, the mother must have been outside the United States throughout the 21 days before conception and the first 20 weeks of pregnancy.

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