Rubella Outbreak -- Westchester County, New York, 1997-1998

Since licensure of rubella vaccines in 1969, the incidence of rubella and congenital rubella syndrome (CRS) in the United States has decreased substantially. Rubella infection during the first trimester of pregnancy can result in miscarriage, stillbirth, or infants with a pattern of birth defects (i.e., CRS) (1). One of the national health objectives for 2000 is to eliminate indigenous rubella and CRS (objective 20.1) (2). During 1997-1998, 524 cases of rubella were reported in the United States (CDC, unpublished data, 1999). This report describes a rubella outbreak in Westchester County, New York, demonstrates the importance of accurately defining and vaccinating at-risk populations to prevent transmission, and underscores how collaboration with community-based organizations can facilitate the development and implementation of control measures.

During the outbreak, a clinical case of rubella was defined as an illness with an acute onset of generalized maculopapular rash, a temperature of greater than 99 F ( greater than 37.2 C), and arthralgia/arthritis, lymphadenopathy, or conjunctivitis. Laboratory confirmation of rubella required a positive serologic test for rubella IgM antibody, a substantial increase in acute- and convalescent-phase titers in serum rubella IgG antibody levels by any standard serologic assay, or isolation of rubella virus (3). A confirmed case of rubella required either laboratory confirmation or meeting the clinical case definition and epidemiologic linkage to a laboratory-confirmed case.

From December 1997 through May 1998, 95 confirmed rubella cases were identified in Westchester County (attack rate: 10.7 per 100,000 population); 79 (83%) were laboratory-confirmed and 16 (17%) were linked epidemiologically to a laboratory- confirmed case. During this period, 333 cases were reported in the United States. The outbreak peaked during mid-January and mid-February (Figure 1). The index case-patient in Westchester County was a 23-year-old man from Mexico who first noticed a rash on December 6, 1997. He was exposed previously to a Hispanic co-worker with rubella in Port Chester, New York, who resided in Connecticut, where there was an ongoing rubella outbreak. Port Chester reported 53 (50%) cases; cases were identified in 14 towns, cities, or villages. The outbreak spread through the county along train lines and through work sites.

The median age of case-patients was 23 years (range: 4 months-59 years); 76% were males aged 16-54 years. Of the 22 female patients, 19 were of childbearing age (15-44 years). Of five (26%) pregnant women, three were infected during the first trimester and elected to terminate their pregnancies. The other pregnant women delivered infants with no CRS. Eighty-eight (93%) patients were foreign born; the median time in the United States was 4 years (range: 12 days-26 years). Among foreign-born patients, 34 (39%) were born in Mexico and 31 (35%) in Guatemala. The remaining 23 (27%) patients were born in Colombia, Dominican Republic, El Salvador, Ecuador, Nicaragua, or Portugal. None of the patients born outside the United States had received rubella vaccine. Of the seven U.S.-born patients, four were aged greater than or equal to 29 years with no history of rubella vaccination, and three were aged less than 1 year and had parents who were born in Latin American countries.

Local health authorities initiated control measures including case and contact investigations, vaccination of contacts and susceptible persons in the community, and increased awareness to screen pregnant women for susceptibility to rubella and asymptomatic infection. Active surveillance for rash illness was conducted at 28 sites in the county, including emergency departments, health departments, and private providers. Health alerts in Spanish and English were sent to all schools and physicians and distributed in Hispanic communities. Although rubella vaccine was available at no cost at the county health department, special clinics, and work sites, only 248 doses were administered during December 6, 1997-February 9, 1998.

To facilitate rubella-control efforts, health department staff identified community leaders and formed partnerships between Hispanic community-based organizations and Hispanic outreach workers from the Westchester County Health Department. These community-based organizations collaborated with the health department to provide targeted educational materials and one-on-one counseling about the importance of rubella vaccination and bilingual personnel for vaccination sites.

The number of sites offering measles, mumps, and rubella (MMR) vaccine was increased by the health department at work sites (e.g., restaurants, landscaping companies, and cleaning services), special vaccination clinics (e.g., churches, day labor pick-up sites, and a mobile van), and at district public health clinics. The number of vaccinations administered increased, and by the end of May 1998, 4539 doses of MMR vaccine had been administered. The last case of rubella associated with the outbreak was identified on May 2, 1998.

Reported by: RM Martin, PhD, AJ Huang, MD, HN Adel, MD, CM Larsen, MPA, CE Daleo, MS, MM Landrigan, MPA, H Martinez, Westchester County Dept of Health, New York. BJ Wallace, MD, J Maffei, PF Smith, MD, State Epidemiologist, New York State Dept of Health. Child Vaccine Preventable Diseases Br, Epidemiology and Surveillance Div; and Community Outreach and Planning Br, National Immunization Program, CDC.

Editorial Note:

The rubella outbreak in Westchester County occurred among young Hispanic adults who were born in countries either without national rubella vaccination programs or where such programs were implemented recently. The demographic characteristics of case-patients were similar to those reported in other recent rubella outbreaks in the United States (4). Most cases occurred among unvaccinated persons aged greater than or equal to 20 years and among persons who were foreign born, primarily Hispanics (63% of reported cases in 1997) (CDC, unpublished data, 1998). Previous community outbreaks were localized in close-knit, circumscribed, Hispanic neighborhoods (CDC, unpublished data, 1997). The Westchester County outbreak differed in that it did not remain localized, but spread to 14 towns, cities, and villages and occurred among eight different Hispanic nationalities. The wide distribution of cases and the multiple Hispanic nationalities made it difficult to identify and access the at-risk population for targeted control measures. Factors that may have contributed to the low receipt of rubella vaccine included difficulty identifying who the leaders were in the Hispanic communities, limited demographic information about the Hispanic communities, and the Hispanic communities' distrust of persons affiliated with the government because of immigration concerns.

In outbreaks of rubella in foreign-born populations, both prevention and control measures require a culturally sensitive approach. Collaboration between health departments and community-based organizations may be useful in effectively informing and mobilizing the at-risk population.

In recent years, rubella vaccination programs have been introduced throughout the Americas to decrease the morbidity and mortality from rubella infections during pregnancy. However, because these programs were only recently implemented, persons who have entered the United States as adults probably are not vaccinated and may be susceptible to rubella. Further decreases in rubella incidence in the United States will require increased vaccine coverage in susceptible populations.

During rubella outbreaks, vaccination is the most effective preventive measure. In the United States, two doses of MMR vaccine are recommended at age 12-15 months and 4-6 years (5). For adults who have not received rubella vaccine, a single dose of a rubella-containing vaccine is considered evidence of immunity (6). Reduction in rubella morbidity in Latin America is expected to lower the number of cases imported from this area and indigenous outbreaks in the United States.

References

1. Orenstein WA, Bart KJ, Hinman AR, et al. The opportunity and obligation to eliminate rubella from the United States. JAMA 1984;251:1988-94.
2. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives--full report, with commentary. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991; DHHS publication no. (PHS)91-50212.
3. CDC. Manual for the surveillance of vaccine-preventable diseases. Atlanta, Georgia: US Department of Health and Human Services, CDC, 1997:11-2.
4. CDC. Rubella and congenital rubella syndrome--United States, January 1, 1991-May 7, 1994. MMWR 1994;43:391-401.
5. CDC. Measles, mumps, and rubella--vaccine use and strategies for elimination of measles, rubella, and congenital rubella syndrome and control of mumps: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1998;47(no. RR-8).
6. ACIP. Update on adult immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1991;40(no. RR-12):17-19.

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