Environmental factors associated with increased cholera cases in low-income districts in Zambia, 2017-2018

Abstract

Introduction: Zambia is a cholera-endemic country and the epidemic in the capital, Lusaka, 2017-2018, caused more than 5,900 cases and 110 deaths. Low-income resident districts in Lusaka are known as hotspots for cholera outbreaks. Among these districts, Kanyama sub-district has been the origin of the outbreaks in Lusaka, 2005-2006, 2016, and 2017-2018. However, spatial factors are associated with the increased number of cholera cases in the Kanyama sub-district; the origin place is still not fully understood. We determined the environmental factors associated with the increased cholera cases in the Kanyama sub-district by using geocoordinate data collected during the outbreak in 2017-2018. Methods: We conducted a retrospective data analysis on geocoordinate data of houses of cholera cases identified in Kanyama sub-district during the outbreak in 2017-2018. Associations between the number of cases in each of the 218 generated zones within Kanyama sub-district and the distribution of environmental factors (e.g., water sources, toilets) were analyzed. Results: A total of 405 cholera cases were identified in 136 zones (62%, 136/218). Zones with cases had significantly larger numbers (median, interquartile range; IQR) of toilets outside houses (56.5, 0-256; vs 35.5, 0-151; p<0.001) and pit latrines (51, 0-194; vs 28; 0-117; p<0.001), while significantly smaller number of water tanks than zones without cases (0, 0-21; vs 0.5, 0-19; p=0.021). The number of cases showed a positive correlation with the number of toilets outside houses (rho=0.307, p<0.001) and pit latrines (rho=0.354, p=0.001). Conclusion: Lack of access to sanitary toilet facilities was associated with the increased number of cholera cases in Kanyama sub-district; the origin place of the recent cholera outbreaks in Lusaka, Zambia. Our study highlighted the importance of targeted public health interventions to the sanitation systems in those areas.