Public Health Dispatch: Measles Epidemic --- Majuro Atoll, Republic of the Marshall Islands, July 13--September 13, 2003

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During July 13--September 13, 2003, a total of 647 clinically diagnosed measles cases* were reported on Majuro Atoll in the Republic of the Marshall Islands (RMI); this is the first measles outbreak reported in RMI since 1988. An additional 74 suspected measles cases are under investigation. This report describes the clinically diagnosed measles cases and the public health response to stop the epidemic. Of the 647 cases, 15 (2%) are laboratory confirmed, either by serology, polymerase chain reaction, or viral culture. The age of patients ranged from 2 weeks to 43 years (median: 12 years); 479 (74%) patients were aged <20 years. The overall measles incidence on Majuro Atoll (estimated 2003 population: 25,097) is 26 cases per 1,000 population. The incidence is highest among infants aged <1 year (160 per 1,000 population), followed by children aged 1--4 years (40).

A total of 58 persons with measles have been hospitalized; three patients have died, including a malnourished child aged 15 months with diarrhea and pneumonia, a woman aged 27 years with pneumonia, and a woman aged 39 years whose immediate cause of death remains unknown. Postmortem examination was not available for any of these patients.

To stop measles transmission, the Ministry of Health in RMI recommended measles, mumps, and rubella vaccine (MMR) for all infants aged 6--11 months and all persons aged 1--40 years who did not have documented proof of measles immunity^†. Before the epidemic, estimated vaccine coverage with 1 dose of MMR was <75% for children aged 1--13 years, according to evaluations of computerized vaccination records and of children screened during the vaccination campaign. As of September 13, a total of 98% of persons aged 6 months--40 years had documentation of receipt of at least 1 dose of MMR. Campaign activities that delivered 16,913 doses included 1) vaccinating health-care and public health workers, 2) vaccinating children at nine vaccination posts across the atoll, 3) delaying the start of the school year until school children were vaccinated and requiring documentation of vaccination for school entry, and 4) conducting neighborhood and house-to-house vaccination in areas where adequate coverage was not reached.

To prevent spread from Majuro Atoll, vaccination campaigns were conducted in other atolls and islands in RMI. The Ministry of Health suspended travel of sea vessels and airlines from Majuro Atoll until vaccination campaigns had been completed in other atolls and islands, and required proof of MMR vaccination for all travelers leaving Majuro Atoll for other atolls or islands or for international destinations. A total of 17 measles cases have been reported from Ebeye Island in Kwajalein Atoll; 10 of these persons were exposed in Majuro Atoll. Two other atolls have reported six cases whose exposure was in Majuro Atoll. Measles surveillance has been enhanced in RMI, other Pacific islands, and in the United States. Spread to other areas in the Pacific and to the United States has been limited; five measles cases in Hawaii, three in Guam, one in Palau, and one in California are believed to be linked to this epidemic.

The source of importation of the measles virus to Majuro Atoll has not yet been determined, but the H1 genotype found in this outbreak is common in Asia, and the specific strain has been reported recently in measles cases from Japan and China (1,2). The Advisory Committee on Immunization Practices recommends that all international travelers be immune to measles because it is endemic or epidemic in many parts of the world, including developed countries (3,4). Persons aged <40 years who are traveling to RMI during the next 60 days should be aware that RMI requires documentation of measles immunity for all departing passengers on international flights. The documentation must fulfill the same age-specific requirements used in the vaccination campaign.

Reported by: J Langridrik, MPH, R Edwards, MPH, K Briand, MBBS, M Konelios, H Neamon, F Nathan, Ministry of Health. A Khalifah, Div of Applied Public Health Training, Epidemiology Program Office; H Nguyen, MPH, Epidemiology and Surveillance Div; Immunization Svcs Div, National Immunization Program; Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; M Marin, MD, R Nandy, MBBS, EIS officers, CDC.

This report is based on data contributed by P Asuo, MD, J Gancio, MD, H Emil, S Alfred, B Pharm, Majuro Hospital, Delap, Majuro Atoll, Republic of the Marshall Islands.

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