Rubella

Current Case Definition for Surveillance

The clinical case definition is: "An illness with all of the following characteristics: (a) acute onset of generalized maculopapular rash, (b) temperature greater than 37.2 C (99 F), if measured, and (c) arthralgia/arthritis, or lymphadenopathy, or conjunctivitis." Cases meeting the measles case definition, or with serology compatible with recent measles infection, are excluded. The laboratory criteria for diagnosis is "isolation of rubella virus, or a significant rise between acute- and convalescent-phase titers in serum rubella immunoglobulin G antibody level by any standard serologic assay, or positive serologic test for rubella IgM antibody." Probable cases must meet the clinical case definition. Confirmed cases must either be laboratory confirmed, or meet the clinical case definition and be epidemiologically linked to a laboratory-confirmed case. Congenital rubella syndrome (CRS) is also reportable.

Immunization

The first rubella vaccines were licensed in the United States in 1969. In 1979, the current RA 27/3 vaccine was licensed and other vaccine removed from the market. The rubella vaccine is usually given combined with the measles and mumps vaccines as MMR. For the rubella vaccine, seroconversion occurs in about 95% of vaccinees after one dose. No significant waning immunity has been demonstrated to date. Immunization is currently required by Maryland law for children entering pre-school programs, kindergarten, and all grades, one through twelve. Based on the 1998/99 retrospective kindergarten survey, an estimated 90% of children in Maryland had received one dose of MMR by 24 months of age (compared to 78% in the 1988/89 survey).

Rubella can be a disastrous disease in early gestation, leading to fetal death, premature delivery, and an array of congenital defects in up to 85% of infants infected in the first trimester. In the pre-vaccine era, epidemics of rubella occurred every six to nine years in the United States, with the last major epidemic in 1964-1965 resulting in 12.5 million cases of rubella and 20,000 cases of CRS. The estimated lifetime cost of one case of CRS today is in excess of $200,000.

In Maryland, the last epidemic of rubella involving thousands of cases was also during 1964, when 3,583 cases were reported. Over 10,000 cases were reported in 1941, the largest epidemic recorded in the state. In contrast, no more than six cases have been reported in any one-year since 1983. Only one case has been reported since the last publication of this report, with onset in 1995.

The last case of CRS in Maryland was reported in 1976. Between 1966 and 1976, 24 cases of CRS were reported in Maryland (but were not included in the numbers of rubella cases reported during these years). CRS was not nationally notifiable prior to 1966, and no data on CRS in Maryland could be found in the EDCP files before 1966.

Figure 1. Reported Cases of Rubella in Maryland, 1970-1998.

Figure 2. Reported Cases of Rubella in Maryland, 1923-Present

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