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Measles outbreak reveals measles susceptibility among adults in Namibia, 2009 - 2011

Ikechukwu U Ogbuanu, Clementine Muroua, Martiena Allies, Kennedy Chitala, Sue Gerber, Primus Shilunga, Petrus Mhata, Jennifer L Kriss, Lucille Caparos, Sheilagh B Smit, Roselina J de Wee, James L Goodson

Abstract


Background. The World Health Organization, African Region, set the goal of achieving measles elimination by 2020. Namibia was one of seven African countries to implement an accelerated measles control strategy beginning in 1996. Following implementation of this strategy, measles incidence decreased; however, between 2009 and 2011 a major outbreak occurred in Namibia.

Methods. Measles vaccination coverage data were analysed and a descriptive epidemiological analysis of the measles outbreak was conducted using measles case-based surveillance and laboratory data.

Results. During 1989 - 2008, MCV1 (the first routine dose of measles vaccine) coverage increased from 56% to 73% and five supplementary immunisation activities were implemented. During the outbreak (August 2009 - February 2011), 4 605 suspected measles cases were reported; of these, 3 256 were confirmed by laboratory testing or epidemiological linkage. Opuwo, a largely rural district in north-western Namibia with nomadic populations, had the highest confirmed measles incidence (16 427 cases per million). Infants aged ≤11 months had the highest cumulative age-specific incidence (9 252 cases per million) and comprised 22% of all confirmed cases; however, cases occurred across a wide age range, including adults aged ≥30 years. Among confirmed cases, 85% were unvaccinated or had unknown vaccination history. The predominantly detected measles virus genotype was B3, circulating in concurrent outbreaks in southern Africa, and B2, previously detected in Angola.

Conclusion. A large-scale measles outbreak with sustained transmission over 18 months occurred in Namibia, probably caused by importation. The wide age distribution of cases indicated measles-susceptible individuals accumulated over several decades prior to the start of the outbreak.


Authors' affiliations

Ikechukwu U Ogbuanu, Global Immunization Division, Center for Global Health, US Centers for Disease Control and Prevention, Atlanta, USA; Department of Immunization, Vaccines and Biologicals, World Health Organization, Geneva, Switzerland

Clementine Muroua, Ministry of Health and Social Services, Windhoek, Namibia

Martiena Allies, Ministry of Health and Social Services, Windhoek, Namibia

Kennedy Chitala, Inter-country Support Team for Eastern and Southern Africa, World Health Organization, Nairobi, Kenya

Sue Gerber, Namibia Country Office, Center for Global Health, US Centers for Disease Control and Prevention, Windhoek, Namibia

Primus Shilunga, Ministry of Health and Social Services, Windhoek, Namibia

Petrus Mhata, World Health Organization Field Office, Oshakati, Namibia

Jennifer L Kriss, Global Immunization Division, Center for Global Health, US Centers for Disease Control and Prevention, Atlanta, USA

Lucille Caparos, Namibia Institute of Pathology, Windhoek, Namibia

Sheilagh B Smit, Centre for Vaccines and Immunology, National Institute for Communicable Diseases, Johannesburg, South Africa

Roselina J de Wee, Office of the World Health Organization Representative in Namibia, Windhoek, Namibia

James L Goodson, Global Immunization Division, Center for Global Health, US Centers for Disease Control and Prevention, Atlanta, USA

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Keywords

Epidemiology; Measles; Epidemic; Outbreak

Cite this article

South African Medical Journal 2016;106(7):715-720. DOI:10.7196/SAMJ.2016.v106i7.10651

Article History

Date submitted: 2016-02-09
Date published: 2016-06-17

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