Measles Outbreak— Netherlands, April 1999—January 2000

Morbidity and Mortality Weekly Report, April 14, 2000

On June 21, 1999, a cluster of five cases of measles was reported among the 390 students attending a religion-affiliated elementary school in the Netherlands. Persons belonging to this religious denomination routinely do not accept vaccination. Municipal health services (MHSs) investigated and found 160 suspected measles cases among children attending the school. By February 4, 2000, 2961 measles cases, including three measles-related deaths, had been reported by 35 MHSs to the national registry. This report summarizes the investigation of the measles outbreak in the Netherlands, which indicated that measles can be a severe disease among unvaccinated populations in the Netherlands.

Measles is a notifiable disease in the Netherlands, and cases that occurred during this outbreak were reported by physicians to the local MHS as part of routine surveillance. The vaccination status of ill persons was reviewed based on written records kept by reporting physicians and sent to the vaccination registry. In April 1999, the first cluster of measles cases occurred, followed by the reported elementary school outbreak in June. No cases of measles with onset in May were reported, and transmission was low during June and July (Figure 1). When schools reopened in August, the number of cases increased. The outbreak peaked during October-November, then decreased rapidly. As of February 4, the last reported cases had onset during the week of January 16. Since then, the number of reported cases has decreased substantially, suggesting that the outbreak is ending.

From April 15, 1999, to February 4, 2000, 2961 cases of measles were reported in 35 (67%) of the country's 52 MHSs; 2317 (78%) were reported by 10 MHSs. All reporting municipalities have large communities affiliated with the religious group. Of the 105 case-patients tested for measles immunoglobulin type M, 100 (95%) had serologically confirmed measles.

Complications among acute measles case-patients were assessed by telephone follow-up with reporting physicians; 510 (17%) cases had one or more complications and/or hospitalizations (Table 1). Three patients died as the result of measles complications: one child aged 2 years had an underlying cardiac disorder and subsequent cardiac failure, one child aged 3 years developed myocarditis, and one adolescent aged 17 years developed kidney failure and acute respiratory distress syndrome. Sixty-eight (2.2%) persons were reported hospitalized: 37 (1.2%) for pneumonia, seven (0.2%) for dehydration, five (0.2%) for encephalitis, four (0.1%) for high fever, three (0.1%) for shortness of breath, two (0.1%) for severe otitis media, two (0.1%) for croup, and six (0.2%) for other reasons. Two persons developed measles while hospitalized for other reasons.

Of the 2882 patients whose ages were known, the median age was 6 years (range: 0-52 years): 95 (3%) were aged [less than]1 year; 949 (33%), aged 1-4 years; 1282 (44%), aged 5-9 years; 382 (13%), aged 10-14 years; 87 (3%), aged 15-19 years; and 87 (3%), aged [geq] 20 years. Information on vaccination status was available for 2907 persons; 2770 (95%) were unvaccinated and 137 (5%) were vaccinated children. Of the 137, 117 (85%) were aged [less than]9 years and all had received one dose of measles, mumps, and rubella vaccine (MMR); in 20(15%) children the number of doses was unknown. Based on data from the national registry, 2749 persons whose ages were known were unvaccinated: 2317(84%) persons eligible for vaccination were not vaccinated for religious reasons and 173(6%) for other reasons (e.g., lack of concern about measles or concern about adverse events); 187(7%) were not eligible for vaccination: 160(85%) were aged [less than]14 months (the recommended age for administration of the first dose of measles v accine), 20(11%) were born before 1976 (the year measles vaccination was introduced), and seven (4%) had a contraindication for measles vaccination. For the remaining 72(3%) unvaccinated persons, the reason for not being vaccinated was unknown.

In response to the outbreak in the Netherlands, on July 1, control activities were implemented, including 1) tracing contacts of cases, 2) offering vaccine or immunoglobulin to susceptible contacts, 3) alerting all secondary-care and tertiary-care hospitals about the measles outbreak, 4) requesting general physicians to report all suspected cases, 5) conducting catch-up vaccination sessions at MHSs and mother and child clinics, 6) increasing media attention about undervaccination, and 7) urging parents to complete vaccination of children.

Reported by: JE van Steenbergen, National Coordination Center for Communicable Disease Outbreak Management; S van den Hof, National Institute for Public Health and the Environment; MW Langendam, Municipal Health Svc, Amsterdam; JHTC van de Kerkhof, Municipal Health Svc, Zuid-Holland Zuid; WLM Ruijs, Municipal Health Svc, Rivierenland, Netherlands. Communicable Diseases and Immunization Unit, European Regional Office, World Health Organization (WHO), Copenhagen, Denmark; Vaccines and Biologicals Dept, WHO, Geneva, Switzerland. Respiratory and Enteric Viruses Br, Div of Viral and Rickettsial Diseases, National