In 1989, the United States established a goal to eliminate indigenous
rubella and congenital rubella syndrome (CRS) by 2000. Reported rubella cases
are at record low levels; however, cases and outbreaks have occurred, primarily
among unvaccinated foreign-born adults.
To evaluate the current epidemiology of rubella and CRS and assess progress
Design, Setting, and Subjects
Analysis of rubella cases reported to the National Notifiable Diseases
Surveillance System from 1990 through 1999 and CRS cases reported to the National
Congenital Rubella Syndrome Registry from 1990 through 1999. Since 1996, US
and international viral isolates have been sequenced.
Main Outcome Measures
Incidence and characteristics of rubella and CRS cases; molecular typing
of virus isolates.
Annually from 1990 through 1999, the median number of reported rubella
cases was 232 (range, 128-1412), and between 1992 and 1999, fewer than 300
rubella cases were reported annually, except in 1998. During the 1990s, the
incidence of rubella in children younger than 15 years decreased (0.63 vs
0.06 per 100 000 in 1990 vs 1999), whereas the incidence in adults
aged 15 to 44 years increased (0.13 vs 0.24 per 100 000). In 1992,
incidence among Hispanics was 0.06 per 100 000 and increased to a
high in 1998 of 0.97 per 100 000. From 1997 through 1999, 20 (83%)
of 24 CRS infants were born to Hispanic mothers, and 21 (91%) of 23 CRS infants
were born to foreign-born mothers. Molecular typing identified 3 statistically
distinct genotypic groups. In group 1, the close relatedness of viruses suggests
that a single imported source seeded an outbreak that did not spread beyond
the Northeast. Similarly, within groups 2 and 3, relatedness of viruses obtained
from clusters of cases suggests that single imported sources seeded each one.
Diversity of viruses found in 1 state is consistent with the conclusion that
several viruses were imported. Moreover, the similarity of viruses found across
the country, combined with a lack of epidemiologic evidence of endemic transmission,
support the conclusion that some viruses that are common abroad, particularly
in Latin America and the Carribean, were introduced into the United States
on several separate occasions.
The epidemiology of rubella and CRS has changed significantly in the
last decade. These changes and molecular typing suggest that the United States
is on the verge of elimination of the disease. To prevent future rubella outbreaks
and CRS, current strategies must be enhanced and new strategies developed.