Measles outbreak and response immunisation in a south-western district of Nigeria: January to June 2013

An outbreak of measles occurred in Olorunda district, Nigeria, between January and June 2013. Outbreak response immunisation (ORI) was conducted as a control measure. We will describe the epidemiology of the outbreak and assess the impact of ORI. We visited all of the health facilities (73) in July 2013 to ascertain the cases through a review of the patient registers and case notes, using the World Health Organization case definition of measles. Data on children vaccinated during ORI were retrieved. To assess the impact of ORI, cumulative measles incidence for the targeted age group (6-59 months) and non-target age group (< 6 months and >= 5 years) was calculated before and after ORI. A total of 94 cases were identified, of which 89% were confirmed by laboratory and epidemiological linkage. More than three quarters (80%) of the confirmed cases were children < 5 years, with a 2% case fatality rate. The outbreak spanned 26 weeks, reaching its peak in week 12. Cases were clustered in the Sabo and Ota Efun wards, with over 88% of the confirmed cases having a zero-dose measles vaccination history. A total of 2 861 children were vaccinated during ORI, with administrative coverage of 10%. The cumulative incidence in the target age prior to ORI was 153.8 per 100 000, which decreased to 27.9 per 100 000 after ORI. The incidence in the non-target age group also decreased from 11.1 per 100 000 before ORI to 2.2 per 100 000 after ORI. Our investigation shows that ORI was effective in the control of the measles outbreak in Olorunda district. Hence, there is need to strengthen the conduct of ORI exercises during a measles outbreak to achieve higher coverage. (C) SAJID