Poliomyelitis outbreak investigation in Kayanza Health District, Burundi, 2023

Introduction: In recent years Africa has been facing epidemics linked to poliovirus derived from the vaccine strain with a predominance of type 2. This situation does not spare Burundi. A case of Acute Flaccid Paralysis was notified on 18 June 2023 from Kayanza district, samples were collected which tested positive for circulating vaccine derived poliovirus type 2 (cVDPV2). We investigated to determine cases' characteristics, to identify possible source of infection, to determine the extent of the outbreak and make recommendations. Methods: This was a cross-sectional study. Data collection was done using Polio investigation form extracted from novel oral polio vaccine type 2 (nVPO2) surveillance guidelines. Review of patient's note, case's household visit, contact tracing and environmental assessment were conducted. Data were analyzed using Excel. A case was defined as any child under 15 years of age with paralytic illness from who poliovirus was isolated and resident of Kayanza district from June to August 2023. Results: The case was a male child living with his parents, aged 18 months, from a family of 2 children of which he is the second, received 4 doses of bivalent oral polio vaccine (bOPV) and one dose of inactivated polio vaccine (IPV). He presented to the clinic on 18 June, 2023 with a sudden paralysis which started on his right leg on June 15, 2023. In the past medical history, the child was on plumpy Nut which is a specific formulated product for the nutritional rehabilitation. The case's household and neighborhood environment were unhygienic. Of 12 contacts found, 67% (8) were male, all (100%) contacts were vaccinated, 75% had vaccination card and 100% of contacts had no symptoms. Conclusion: Our study shows that there could be link between the case and the unhygienic environment he lived in. The child received only one dose of IPV which was inadequate to protect against polio according to CDC. The case was malnourished which could have further predisposed him to getting poliomyelitis. It is necessary to initiate environmental surveillance of polio in the area and introduce one or two more inactivated polio vaccine doses in the routine vaccination schedule.