Measles outbreak investigation in an urban slum of Kaduna Metropolis, Kaduna State, Nigeria, March 2015.

Introduction: Despite availability of an effective vaccine, the measles epidemic continue to occur in Nigeria. In February 2015, we investigated a suspected measles outbreak in an urban slum in Rigasa, Kaduna State, Nigeria. The study was to confirm the outbreak, determine the risk factors and implement appropriate control measures.

Methods: We identified cases through active search and health record review. We conducted an unmatched case-control (1:1) study involving 75 under-5 cases who were randomly sampled, and 75 neighborhood controls. We interviewed caregivers of these children using structured questionnaire to collect information on sociodemographic characteristics and vaccination status of children. We collected 15 blood samples for measles IgM using Enzyme Linked Immunosorbent Assay. Descriptive, bivariate and logistic regression analyses were performed using Epi-info software. Confidence interval was set at 95%.

Results: We recorded 159 cases with two deaths {case fatality rate = 1.3%}. 50.3% (80) of the cases were male. Of the 15 serum samples, 11(73.3%) were confirmed IgM positive for measles. Compared to the controls, the cases were more likely to have had no or incomplete routine immunization (RI) [adjusted odds ratio (AOR) (95% confidence interval (CI)]: 28.3 (2.1, 392.0), contact with measles cases [AOR (95% CI)]: 7.5 (2.9, 19.7), and having a caregiver younger than 20 years [AOR (95% CI)]: 5.2 (1.2, 22.5). Measles serum IgM was positive in 11 samples.

Conclusion: We identified low RI uptake and contact with measles cases as predictors of measles outbreak in Rigasa, Kaduna State. We recommended strengthening of RI and education of care-givers' on completing RI schedule.