Rubella outbreak investigation in North Bench District, Southwest Ethiopia, 2024

Abstract

Introduction: Rubella poses severe risks to pregnant women due to the potential for Congenital Rubella Syndrome. In Ethiopia, rubella remains an overlooked public health concern. The disease is not a priority in national surveillance, and its vaccine has yet to be included in the infant immunisation program. On January 8, 2024, a rumour of a suspected rubella outbreak in Southwest Ethiopia was reported, with rising cases, prompting a study to confirm the existence of the outbreak, describe cases epidemiologically, and assess risk factors. Methods: A descriptive cross-sectional study combined with a 1:1 unmatched case-control investigation was conducted in the North Bench district, Ethiopia, from July 10 to 30, 2024. The descriptive analysis included all 415 cases from the outbreak line list. The case-control study enrolled 143 cases and 143 controls. Cases were defined as individuals with laboratory-confirmed rubella IgM, epidemiologically linked to confirmed cases, or presenting with fever and maculopapular rash in the affected kebeles from January 8 to May 26, 2024; randomly selected from the line list. Controls were selected from rash- and fever-free neighbours. Variables with P<0.25 in bivariable analysis entered multivariable logistic regression; those with P<0.05 were deemed significant predictors of rubella infection. The adjusted odds ratios and 95% confidence intervals were reported. Results: Rubella outbreak was confirmed in the district, and it had an overall attack rate of 34.8 per 10,000 population. Having a history of contact with an active case (aOR: 3.8, 95%CI: 2.2- 6.6), having a history of diarrhea before two weeks (aOR: 2.7, 95%CI: 1.5-4.6), families with a size of more than 5 per household (aOR: 2.2, 95%CI: 1.2-3.9), lacking vitamin A supplementation in the past six months (aOR: 1.8, 95%CI: 1.1 – 3.1), and living in a poorly ventilated house (aOR: 1.8, 95%CI: 1.0- 3.2) were found to be associated with rubella infection. Conclusion: Rubella outbreak was confirmed in the district, and was associated with contact with cases, recent diarrhoea, large households, poor ventilation, and lack of vitamin A. Improving vitamin A coverage, early case detection, and community awareness on ventilation and infection prevention are essential to prevent future outbreaks