CONTROL OF A COMMUNITY OUTBREAK OF MEASLES WHICH STARTED IN A POORLY IMMUNIZED HIGH-SCHOOL POPULATION

An outbreak of measles occurred in Darwin from February to March 1991. The first case was in a 13-year-old high school student who had retur ned from a holiday overseas. She was symptomatic on the second day of the new school term. She infected an infant while both waited in a doc tor's surgery. Outbreak control measures were instituted 18 days later when the Communicable Diseases Centre was first alerted of cases thro ugh the laboratory notification scheme. Through active surveillence, w e identified 76 cases of measles, of whom 92 per cent (70 cases) were under 20 years of age. Of these, 46 were students at the index high sc hool in which the attack rate was 39.2 per 1000. They transmitted the disease to six unvaccinated siblings aged 11 to 18 years, resulting in a secondary attack rate of 113 per 1000 in this age group (relative r isk of disease in siblings 2.8, 95 per cent confidence interval 1.2 to 6.2). The outbreak affected one other high school, a number of primar y schools, one tertiary institution, and nine children under five year s. Only four of the cases had a verified history of previous immunisat ion against measles. The outbreak was arrested within two weeks of ins tituting community-wide control measures. Inadequate immunisation cove rage among school-aged children and delays in notification contributed to the severity of the outbreak. Improved measles surveillance system s, including telephone notification of clinical cases are needed so th at control measures can be instituted immediately within the household and in the community.