Title : Measles outbreak investigation in korotou health area, dianra health district, Côte d’Ivoire, april-may 2025

Background: Measles remains a major cause of morbidity and mortality among children despite the availability of an effective vaccine. In Côte d’Ivoire, outbreaks continue to occur in rural areas. In April 2025, an outbreak of confirmed measles cases was reported in Korotou health area, Dianra health district. This study aimed to describe the outbreak and identify associated risk factors.

Methods: We conducted a retrospective unmatched case-control study (1:3 ratio) from April 12 to May 31, 2025. A case was defined as any laboratory-confirmed measles infection (IgM positive) in a resident of Korotou during the study period. Controls were healthy individuals selected from the same community. Data on sociodemographic characteristics, vaccination status, and exposures were collected using structured questionnaires, medical record review, and observation. Data were analyzed using Epi Info 7.2. Odds ratios (OR) with 95% confidence intervals (CI) were calculated.

Results: A total of 60 children were included (20 cases and 60 controls), with an attack rate of 5.4%. The median age was 3 years in both groups. Children aged 1-4 years and males represented 70% of participants. Among cases, 80% were unvaccinated or partially vaccinated compared to 20% among controls. Incomplete or absent vaccination was strongly associated with measles infection (OR = 16; 95% CI: 4.19- 61.10; p < 0.001). Contact with a confirmed case was the strongest risk factor (OR = 162; 95% CI: 251050; p < 0.001). Recent travel was also significantly associated with infection (OR = 5.44; 95% CI: 1.79- a16.54; p = 0.003). No significant association was found with nutritional status or vitamin A supplementation.

Conclusion: The outbreak was driven mainly by low vaccination coverage, contact with infected individuals, and recent mobility. Children aged 1-4 years were the most affected. Strengthening routine immunization, surveillance, and outbreak response is essential to prevent future outbreaks.

Keywords: Measles, outbreak investigation, case-control study, vaccination, Côte d’Ivoire

KOFFI Koidio Marcel Venance is a State Registered Nurse and Health Data Manager working as Surveillance Officer at the Regional Directorate of Health and Public Hygiene of Béré, Côte d’Ivoire. He is a graduate of the FETP Frontline and Intermediate programs and serves as an FETP mentor. He specializes in disease surveillance, data management, and outbreak investigation and response. He has participated in international scientific conferences, including the Pan-African Society of Public Health Conference and EMOIS 2025 (Nancy, France). In 2025, he was ranked 3rd best surveillance officer in Côte d’Ivoire.