Spatial Dynamics and High Risk Transmission Pathways of Poliovirus in Nigeria 2001-2013.

Area of Science:

• Epidemiology
• Mathematical modeling
• Public health

Background:

• Nigeria's polio eradication program achieved significant success, reducing cases to six in 2014 and zero in 2015.
• Despite progress, predicting and managing future polio outbreaks remains a critical concern.

Purpose of the Study:

• To model poliovirus spread in Nigeria using spatial connectivity and human mobility data.
• To identify key factors influencing polio incidence and transmission networks between local government areas (LGAs).

Main Methods:

• A Poisson mixed effects model was employed to analyze poliovirus spread from January 2001 to November 2013.
• Three human mobility models (distance, gravity, radiation) were used to estimate connectivity between LGAs.
• Explanatory variables like under-five population and seasonality were investigated; model fit was assessed via simulation.

Main Results:

• Spatial connectivity, the number of unvaccinated children under five, and season were significantly associated with polio incidence (P < 0.001).
• The radiation model best described human mobility and poliovirus spread, outperforming distance and gravity models (P < 0.05).
• Inferred transmission networks were predominantly local, with most secondary spread occurring within 10 km of the source LGA.

Conclusions:

• Poliovirus transmission in Nigeria is largely localized between geographically adjacent areas.
• High-probability transmission pathways, particularly those involving high population movement, are crucial for understanding spread.
• Outbreak response strategies must incorporate knowledge of these localized transmission dynamics to effectively protect vulnerable populations.