Congenital rubella syndrome in the United States, 1970-1985. On the verge of elimination.

The National Congenital Rubella Syndrome Registry, a passive surveillance system, and the Birth Defects Monitoring Program, a newborn hospital discharge data set, are used to monitor the incidence of congenital rubella syndrome in the United States. Reports to the registry contain clinical and laboratory data which allow cases to be classified into six categories according to the likelihood of having congenital rubella syndrome. The monitoring program records newborn discharge diagnoses, without detailed information, of a nonrandom sample of about one fourth of the births in the United States annually. To evaluate the two systems and to estimate the actual incidence of congenital rubella syndrome, the authors collected hospital discharge summaries on all cases as reported by the monitoring program from 1970-1985 and classified them by the registry criteria. Of the 392 cases reported to the monitoring program during 1970-1985, 24% (n = 93) could be classified as confirmed or compatible compared with 79% (n = 415) of the 526 cases reported to the registry (rate ratio = 3.3; 95% confidence interval (CI) 2.9-3.8). Diagnosis of congenital rubella syndrome was made during the neonatal period for 68% (263 of 389) registry cases for whom such data were available. When the Lincoln-Peterson capture-recapture method of estimating population size for independent surveillance systems was used, an estimated 1,064 confirmed and compatible cases (95% CI 668-1,460) diagnosed during the neonatal period occurred during 1970-1979, for an average of 106 cases per year. During 1980-1985, an estimate of 122 neonatal confirmed and compatible cases (95% CI 8-236) occurred, for an average of 20 cases per year. A downward secular trend in the incidence of congenital rubella syndrome beginning in 1980 was observed. The registry detected 22% of all neonatal confirmed and compatible cases, the monitoring program detected 8%, and the two systems combined detected a total of 28%. The results indicate that congenital rubella syndrome may be on the verge of elimination in the United States.