Measles outbreak among school-aged children - Juneau, Alaska, 1996

Morbidity and Mortality Weekly Report, Sept 13, 1996

An outbreak of measles among school-aged children occurred in Juneau, Alaska, from February 16 through April 25, 1996. Of 63 confirmed cases(*), 47 were serologically confirmed, and virus was cultured from 15; a total of 41 (65%) were among school-aged children (i.e., aged 6-18 years). This report summarizes results of the epidemiologic investigation conducted by the Division of Public Health, Alaska Department of Health and Social Services (ADPH), which found evidence of measles transmission at schools despite high rates of coverage with one dose of measles-containing vaccine (MCV).

The first five cases occurred among four students and a teacher at an elementary school; all had rash onset during February 16-19. The 63 case-patients ranged in age from 8 months to 45 years (median: 11 years): one was aged <1 year; 10 (16%), 1-4 years; 41 (65%), 5-19 years; and 11 (18%), [greater than or equal to]20 years. Two persons with measles were hospitalized, including a child with dehydration and an adult with neutropenia. Measles virus was isolated from nasopharyngeal specimens obtained from 15 patients and from urine specimens from three of these same patients; isolates were genotypically similar to viruses recently isolated from Europe but different from isolates circulating in the United States during 198a1992 (1).

Probable sites of measles acquisition were school (31 [49%l), home (14 [22%]), indoor soccer games (seven [11%]), and other settings (six [10%]); the site was unknown for five (8%). Cases were more likely. to have been acquired at school during the first 35 days of the outbreak (19 [59%] of 32) than during the remaining 35 days (12 [39%] of 31).

Cases occurred among 40 students and four faculty members at seven of eight public schools in Juneau; one case occurred in a student at a private school. School-specific incidence rates were highest at the high school annex([dagger]) (five [4%] of 127), a middle school (15 [2%] of 687), and the elementary school attended by the index patient (seven [1%] of 525). At the beginning of the 1995-96 school year, approximately 99% of 5400 public school children in Juneau had received at least one dose of MCV. The number of children who had received more than one dose of MCV was unknown; however, a second dose of measles-mumps-rubella vaccine (MMR) for school-aged children enrolled in public or private school was not required in Alaska at the time of the outbreak.

Of the 63 case-patients, 33 (52%) had received only one dose of MCV on or after their first birthday, and 30 (48%) had never been vaccinated with MCV. Among the 30 who were not vaccinated, 24 (80%) were eligible to be vaccinated (i.e., aged [greater than or equal to]12 months and born on or after January 1, 1957); of the 24 who were eligible to be vaccinated, all 12 school-aged children had religious exemptions, and two of nine children aged 1-4 years were siblings of these unvaccinated schoolchildren.

Although no source case was identified, this outbreak coincided with a measles outbreak associated with the Seattle-Tacoma (Washington) airport, the major airport gateway to Juneau. The first three case-patients in the Seattle area had onset of measles during February 2-4, 1996; these cases occurred among two airport workers and an airport visitor who, on January 20, were at the Seattle-Tacoma airport concourse of the main airline serving Juneau. Because measles transmission probably occurred in the airport on January 20, a Juneau-bound passenger also may have been exposed and may have become the source case for the Juneau outbreak. Isolates from the Seattle cases were not available for comparison.

Measures to control the outbreak were implemented beginning February 17 and included efforts to vaccinate school-aged children and contacts of persons with suspected cases with at least one dose of MCV; active surveillance for rash illness in doctor's offices, schools, and the one hospital emergency department in Juneau; and weekly fax transmissions of outbreak updates to health-care providers and public health nurses in Juneau and all other areas of southeast Alaska. As a result of this outbreak, ADPH is requiring all Alaska schoolchildren in kindergarten and first grade to receive a second dose of MCV for school entry.

Reported by: P Rohrbacher, K Miller, MPH, L Cameron, M Lexon, C See, K Slotnick, J Miller, M O'Bryan, G Herriford, K Glass, T Schmidt, MS, W Evans, P Kunkel, B Bond, MS, J Maddux, DVM, M Masters, PhD, M Westcott, D Ritter, S Kew, L Wood, MPA, G Yett, SA Jenkerson, MSN, M Schloss, MPH, E Funk, MD, M Beller, MD, P Nakamura, MD, JP Middaugh, MD, State Epidemiologist, Div of Public Health, Alaska Dept of Health and Social Svcs. J Boase, MS, Seattle-King County Health Dept Seattle; B Lamont, Washington Dept of Health. Measles Virus Section, Respiratory and Enterovirus Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Measles Activity, Child Vaccine Preventable Disease Br, Div of Epidemiology and Surveillance, National Immunization Program; Div of Applied Public Health Training (proposed), Epidemiology Program Office, CDC.