Determinants of transitions in water and sanitation services in two urban slums of Nairobi: A multi-state modeling approach.

Access to improved water, sanitation, and hygiene (WASH) services at the household level remains a good strategy to improve the health and well-being of individuals. Informal settlements, such as urban slums, are at risk of the spread of diseases due to the relative lack of access to safe, clean drinking water and basic sanitation, as well as poor hygiene. Global initiatives, such as the Sustainable Development Goals (SDGs) adopted by the United Nations, are aimed at transitioning households and communities from unimproved to sustained improved states of WASH services. To deepen understanding of the time dynamics between states of WASH services in the Nairobi Urban and Demographic Surveillance System (NUHDSS), this study employs the multi-state transition model to assess the influence of potential risk factors on these transitions. Results indicated that study sites, wealth tertile, age of household head, poverty status, the ethnicity of household head, household ownership, and food security were associated with household transitions of WASH services. There was a lower probability for households to transition from unimproved to improved toilet services than the reverse transition, but a higher chance for households to transition from unimproved to improved water and garbage services. The estimated average time that households spent in the unimproved and improved states before transitioning were, respectively, 35 months and 9 months for toilet services, 7 months and 66 months for water services, and 16 months and 19 months for garbage services. Thus, households tend to remain longer in the unimproved state of toilet and garbage services, and when in the improved states, they transition back relatively faster compared to water services. In conclusion, sanitation services in Nairobi informal settings remain largely unsatisfactory as transitions to improved services are not sustained. It is therefore important for governments, policy-makers, and stakeholders to put in place policies and interventions targeting vulnerable households for improved and sustained WASH services.