Measles reporting completeness during a community-wide epidemic in inner-city Los Angeles

A study was undertaken to determine the extent of measles underreporting among preschool-age children. In two community surveys conducted in inner-city Los Angeles during 1990 and 1991, respondents were asked whether preschool-age children in their households had ever been ill with measles. Information about measles episodes was obtained and medical records were reviewed, when available. A probable measles case was defined as having 3 or more days of rash with fever of 38.3 degrees centigrade or greater, and either cough, coryza, or conjunctivitis. To determine the proportion of cases reported, probable measles cases identified were matched with measles cases reported to the Los Angeles County Department of Health Services. Of the 947 children ages 6 weeks through 59 months included in the surveys, 35 children had experienced an illness episode which met the probable measles case definition. Ten (29 percent) of the 35 probable measles cases were reported to the health department. Hospitals reported 9 (69 percent) of 13 probable measles cases evaluated while private physicians' offices reported 0 (0 percent) of 12 evaluated (Fisher's exact test, P < 0.001), although 5 children were seen by private physicians before rash onset. Reporting was more complete for cases occurring during 1990 and 1991 (33 percent) than from 1987 through 1989 (18 percent). The hospitalization rate for preschool-age children with probable measles cases in the catchment area was estimated to be 8 percent (95 percent confidence interval = 0 to 18 percent). Although measles is a serious communicable disease which is almost completely preventable, cases of it among preschool-age children in this high incidence area were substantially underreported,especially by private physicians. Due to reporting bias, reported measles cases were representative of more severe cases than all the cases that occurred.