Measles outbreak investigation in Kambia District, Sierra Leone-2018

Abstract

Background: Measles, an acute highly infectious viral disease, remains one of the leading causes of childhood morbidity and mortality worldwide. Despite the availability of safe and effective vaccines, measles cases have been reported in Sierra Leone. On 29 October 2018, the Kambia district health management team was notified of a suspected measles outbreak. On 1 November 2019, we investigated the outbreak to confirm the diagnosis, assess the magnitude, identify potential risk factors, and institute control measures. Methods and materials: We defined a suspected case as any person with fever and maculopapular rash in Kambia district from 1st October 2018 and a probable case as any suspected case with epidemiologic link to a laboratory confirmed case. We reviewed medical records, interviewed parents, patients and collected blood samples for measles confirmation. We collected patients’ demographic, clinical and exposure history. We conducted active case search and needs assessment for measles reactive mass vaccination in the community. We conducted social mobilization and risk communication. Results: A total of 91 cases (14 laboratory-confirmed and 77 probable cases) with no deaths reported. The overall Attack Rate (AR) was 24.2/100,000 persons, with the highest AR (119.6/100,000 persons) among the 6–11 months age group. The median age was 24.5 months (range 4–348), and 48 (56%) were females. Four out of seven chiefdoms were affected and Gibnleh-Dixon chiefdom was the most affected (AR = 274.9/100,000). The first four detected cases had travel history to the neighboring Republic of Guinea, where there was a confirmed measles outbreak, and three of the four affected villages are close to the border. The district administrative vaccination coverage was 87%, however, of the total 84 eligible cases, only two had vaccination cards. Conclusion: A measles outbreak was confirmed in Kambia district which shares a border with Guinea. The importation of measles cases in a susceptible community might have contributed to the spread of measles in the affected chiefdoms. A reactive mass vaccination targeting children aged six months to 15 years was conducted and achieved coverage of 100.8%. We recommended strengthening routine immunization through increased outreach vaccination sessions to communities, supplementary vaccination and to strengthen cross border surveillance and response framework.