Seasonal variation, temporal trends, and factors associated with PCR-confirmed cholera in Goma city and surrounding health zones in Eastern Democratic Republic of the Congo, 2020-2024: a multilevel analysis.

INTRODUCTION

Cholera remains a persistent public health challenge in Goma, Eastern Democratic Republic of the Congo. This study assessed seasonal variation, temporal trends, and factors associated with PCR-confirmed cholera in Goma city and surrounding health zones (2020-2024) using a multilevel analytical approach to support targeted public health interventions.

METHODS

We analysed 18,929 patients tested for cholera by PCR between 2020 and 2024. Age, sex, season, year, and health zone were examined. Environmental, WASH-related, and intervention-related variables were unavailable in the surveillance database and, therefore, could not be included. Multilevel mixed-effects logistic regression assessed factors associated with PCR positivity, accounting for clustering at the health zone level and seasonal effects.

RESULTS

Overall PCR positivity rate was 32.5%. Children aged 5-9 years and 10-14 years had the highest positivity rate (40.9% and 38.9% respectively), while < 5 years showed the lowest (29.2%). More patients were tested in the rainy season (66.2%), with a higher positivity rate compared to the dry season (34.8% vs. 27.9%, p < 0.001). Positivity rate varied across health zones (Goma: 36.0%; Karisimbi: 28.8%) and increased over time (2020: 17.2%; 2024: 37.8%, p < 0.001). Monthly analysis revealed pronounced peaks in 2023-2024, particularly during the rainy season. Multilevel modelling indicated that season, calendar year, and age were independent predictors of PCR positivity, with modest-to-moderate effect sizes. Residual clustering at the health-zone level was low (ICC 0.002-0.003), indicating that only a small proportion of unexplained variance remained attributable to between-zone differences after adjustment. The season-by-year interaction identified the highest PCR positivity during the 2023 rainy season.

CONCLUSIONS

PCR-confirmed cholera in Goma city and surrounding health zones showed marked seasonal and temporal variation, with children disproportionately affected. These findings support targeted prevention before the rainy season and strengthened surveillance in high-risk areas.