Reporting efficiency during a measles outbreak in New York City, 1991

Objectives. During an epidemic of measles among preschool children in New York City, an investigation was conducted in 12 city hospitals to estimate reporting efficiency of measles to the New York City Department of Health. Methods. Measles cases were identified by review of hospital emergency room and infection control logs and health department surveillance records. The Chandra Sekar Deming method was used (1) to estimate the total number of measles cases in persons less than 19 years old who presented to the 12 hospitals from January through March 1991 and (2) to estimate reporting efficiency. Information on mechanisms for reporting measles cases was collected from hospital infection control coordinators. Results. The Chandra Sekar Deming method estimated that 1487 persons with measles presented to the 12 hospitals during the study period. The overall reporting efficiency was 45% (range = 19% to 83%). All 12 hospitals had passive surveillance for measles; 2 also had an active component. These 2 hospitals had the first and third highest measles reporting efficiencies. Conclusions. The reporting efficiency of measles cases by New York City hospitals to the health department was low, indicating that the magnitude of the outbreak was substantially greater than suggested by the number of reported cases.