Abstract
The polio eradication programme in Nigeria has been successful in reducing incidence to just six confirmed cases in 2014 and zero to date in 2015, but prediction and management of future outbreaks remains a concern. A Poisson mixed effects model was used to describe poliovirus spread between January 2001 and November 2013, incorporating the strength of connectivity between districts (local government areas, LGAs) as estimated by three models of human mobility: simple distance, gravity and radiation models. Potential explanatory variables associated with the case numbers in each LGA were investigated and the model fit was tested by simulation. Spatial connectivity, the number of non-immune children under five years old, and season were associated with the incidence of poliomyelitis in an LGA (all P < 0.001). The best-fitting spatial model was the radiation model, outperforming the simple distance and gravity models (likelihood ratio test P < 0.05), under which the number of people estimated to move from an infected LGA to an uninfected LGA was strongly associated with the incidence of poliomyelitis in that LGA. We inferred transmission networks between LGAs based on this model and found these to be highly local, largely restricted to neighbouring LGAs (e.g. 67.7% of secondary spread from Kano was expected to occur within 10 km). The remaining secondary spread occurred along routes of high population movement. Poliovirus transmission in Nigeria is predominantly localised, occurring between spatially contiguous areas. Outbreak response should be guided by knowledge of high-probability pathways to ensure vulnerable children are protected.
Highlights
The World Health Assembly determined in 1988 that paralytic poliomyelitis would be eliminated from the 125 infected countries by the year 2000 [1]
We considered serotype 1 cases only, as no cases of poliomyelitis due to serotype 3 have been detected in Nigeria since 16th November 2012
We estimated the numbers of each type of oral poliovirus vaccine (OPV) received by a child with acute flaccid paralysis (AFP) by multiplying the total number of doses reported during the initial case investigation by the proportion of supplementary immunisation activities (SIA) in their local government areas (LGA) between the child’s date of birth and onset of paralysis that used the corresponding type of OPV [12]
Summary
The World Health Assembly determined in 1988 that paralytic poliomyelitis would be eliminated from the 125 infected countries by the year 2000 [1]. Despite great successes in eliminating polio in Europe, the Americas and parts of Asia by the Global Polio Eradication Initiative (GPEI), a few remaining endemic countries continue to support poliovirus transmission. Disease burden from the three wild poliovirus serotypes has fallen from 350,000 cases worldwide. Gates Foundation (grant P20064) awarded to Professor Grassly
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
