Modelling Salmonella Typhi in high-density urban Blantyre neighbourhood, Malawi, using point pattern methods

Area of Science:

• Epidemiology
• Spatial statistics
• Public health

Background:

• Salmonella Typhi causes typhoid fever, transmitted via the faecal-oral route.
• Understanding spatial risk factors is crucial for targeted typhoid fever interventions.
• Previous studies have not fully explored spatial variations in typhoid risk within specific communities.

Purpose of the Study:

• To model the spatial variation in typhoid fever risk in Ndirande township, Blantyre.
• To identify individual-level and environmental factors associated with typhoid fever incidence.
• To assess the impact of Water, Sanitation, and Hygiene (WASH) improvements on typhoid risk.

Main Methods:

• Utilized health facility data from 2016 to 2020.
• Developed a marked inhomogeneous Poisson process model.
• Incorporated individual and environmental risk factors into the spatial model.

Main Results:

• Typhoid fever cases exhibited significant spatial clustering.
• A unit increase in the Water, Sanitation, and Hygiene (WASH) score was associated with a 54% decrease in typhoid incidence.
• Typhoid fever intensity was higher in children under 18 compared to adults.
• No strong evidence of temporal variation in typhoid incidence was found.

Conclusions:

• Point pattern models are effective for characterizing spatial variations in disease risk.
• Improving WASH conditions is a critical strategy for reducing typhoid fever burden.
• Spatial analysis highlights vulnerable populations, such as children, for targeted public health efforts.