Spatial and Genomic Data to Characterize Endemic Typhoid Transmission.

Area of Science:

• Environmental microbiology
• Epidemiology
• Genomics

Background:

• Salmonella Typhi (S. Typhi) transmission pathways remain unclear despite known environmental exposures.
• Understanding dominant transmission routes is crucial for controlling typhoid fever in endemic areas.

Purpose of the Study:

• To investigate typhoid fever transmission dynamics using integrated spatial, genomic, and hydrological data.
• To identify high-incidence areas and transmission links in Blantyre, Malawi.

Main Methods:

• Recruited 546 typhoid fever patients and collected blood cultures.
• Geolocated patient households and whole-genome sequenced 256 S. Typhi isolates.
• Employed geostatistical modeling with multidimensional scaling, incorporating genomic and physical distances.

Main Results:

• Typhoid fever incidence varied significantly across Blantyre (<15 to >100 cases per 100,000 population).
• Significant correlations were found between S. Typhi genomic distance and physical household distance (P=.001).
• River catchment analysis improved spatial pattern modeling (P=.003), indicating transmission at smaller scales (<192m).

Conclusions:

• Hydrological systems play a significant role in S. Typhi transmission.
• Integrated genomic and spatial data effectively identify high-incidence zones and transmission connections.
• Findings support targeted environmental surveillance for typhoid control strategies.