Spatial Distribution and Surveillance Performance of Acute Flaccid Paralysis Cases in Rivers State, Nigeria, 2023: A Retrospective Surveillance Data Analysis

Abstract

Background:
Geographic variation in acute flaccid paralysis (AFP) detection and investigation can reveal local surveillance gaps that are obscured by statewide averages. The study assessed the distribution of AFP cases and surveillance performance across local government areas (LGAs) in Rivers State, Nigeria, in 2023.

Methods:
The study conducted a retrospective analysis of routinely collected AFP surveillance line-list data. LGA-level case counts and proportions meeting notification, investigation, stool-timing, and recorded specimen-adequacy indicators were described. Wilson 95% confidence intervals (CIs) were calculated for statewide proportions. LGAs were compared with the programme target of at least 80%. Because population denominators and final non-polio AFP classifications were unavailable, the analysis described case distribution rather than incidence or non-polio AFP rates.

Results:
A total of 423 AFP cases were reported from all 23 LGAs. The median number per LGA was 17 (interquartile range 15–23; range 7–27). Bonny and Omuma reported 27 cases each, followed by Tai (25) and Ikwerre (24); the five highest-count LGAs contributed 126 cases (29.8%). Overall, 411/423 cases (97.2%, 95% CI 95.1–98.4) were notified within seven days and 411/423 (97.2%, 95% CI 95.1–98.4) within 48 hours. Second stool specimens were collected within 14 days for 421/423 cases (99.5%), and 422/423 (99.8%) were recorded as having adequate specimens. Twenty-one LGAs met the 80% notification target. Ogba/Egbema/Ndoni (14/20; 70.0%) and Ahoada East (5/7; 71.4%) did not; Ogba/Egbema/Ndoni accounted for 6 of the 12 delayed notifications statewide. All LGAs met the 80% investigation target.

Conclusions:
AFP surveillance performance in Rivers State was high in 2023, but delayed notification was concentrated in a small number of LGAs. Statewide averages should therefore be complemented by routine LGA-level review, targeted supportive supervision, and investigation of local barriers in Ogba/Egbema/Ndoni and Ahoada East. Population-linked data and final case classifications are needed for assessment of surveillance sensitivity and true spatial risk.