Drivers of acute flaccid paralysis (AFP) surveillance performance: insights from a surveillance peer review in high- and low-performing districts in Zimbabwe

¹Word Health Organization Zimbabwe Country Office, Harare, Zimbabwe

^&Corresponding author
Maxwell Rupfutse, Word Health Organization Zimbabwe Country Office, Harare, Zimbabwe

Introduction    

Poliovirus remains a global health threat, and the Global Polio Eradication Initiative (GPEI) drives coordinated efforts to eliminate it [1-3]. As endemic wild poliovirus transmission narrowed down to two countries (Afghanistan and Pakistan, in the WHO Eastern Mediterranean Region), countries that are already WPV-free are required to maintain highly sensitive surveillance to verify continued absence of circulation and to trigger rapid response to any imported wild virus or emergent variants [1,3]. Polio surveillance is an established system that enables the timely detection and response to poliovirus transmission, forming the foundation of eradication efforts [4,5]. Polio surveillance has three key components including AFP surveillance - the primary system, detecting acute flaccid paralysis in children and confirming poliovirus through stool testing in a WHO accredited laboratories -, and two complementary systems including Environmental Surveillance, which tests wastewater/sewage in targeted areas to identify silent virus circulation, and Immunodeficiency-associated vaccine-derived poliovirus (iVDPV) surveillance which is an AFP surveillance monitoring individuals with immunodeficiency disorder [4].

In Zimbabwe, the Ministry of Health and Child Care (MoHCC) has adopted WHO standards to strengthen its Integrated Disease Surveillance and Response (IDSR) strategy, incorporating VPD surveillance, including AFP surveillance as a critical element. The country's national immunization policy emphasizes the need for a robust vaccine-preventable disease surveillance, and the national AFP surveillance guidelines highlight continuous case-based surveillance, supported by laboratory confirmation and effective data use at all levels [6]. Within the broader VPD surveillance framework [7], Acute Flaccid Paralysis (AFP) surveillance serves as a specialized and highly sensitive system to detect poliovirus transmission. It is the gold standard for detection globally [4,5]. WHO defines AFP surveillance as the systematic identification, investigation, and reporting of all cases of sudden onset flaccid paralysis in children under 15 years, regardless of the cause, to ensure prompt response to possible poliovirus circulation [4,5]. In Zimbabwe, AFP surveillance is guided by the national AFP guidelines and WHO benchmarks, including the detection of at least 2 (in non-outbreak context), and 3 (in outbreak context) non-polio AFP cases per 100,000 children under 15 years and the collection of adequate stool specimens within 14 days of paralysis onset [5,6].

Over the past decade, Zimbabwe has made commendable progress in strengthening its AFP surveillance system. As per Zimbabwe DHIS2, between 2022 and 2025, the country consistently met or exceeded the WHO's minimum performance indicators at the national level. The non-polio AFP rate often surpassed 2 per 100,000, and 3 since the current variant outbreak response initiated in October 2023, reflecting a high level of sensitivity, while stool adequacyanother critical quality indicatorremained above the 80% target nationally. The AFP surveillance peer reviews aim to assess the system's effectiveness, identify strengths and gaps, and recommend actionable improvements. The Global Polio Surveillance Action Plan [8] highlights the need for internal and external reviews to ensure surveillance sensitivity and data quality for program success. Despite Zimbabwe's consistent achievement of the two core AFP surveillance indicators at the national level, ZDHIS2 and internal program reviews show that over the past three years, sub-national performance remains uneven. Periodic desk review of data shows gaps at the district level. These include underreporting of AFP cases, failure to meet both core indicators in several districts, non-polio enterovirus (NPENT) isolation rates falling below the 10% benchmark, and delays in the timely detection, of AFP cases.

Additionally, according to the Zimbabwe Integrated Supportive Supervision (ISS) data, the frequency of active case searches, especially in high-priority areas, has been sub-optimal compared to the required visits. These disparities underscore the need to understand the drivers of performance across districts, guiding targeted improvements and sustaining high-quality AFP surveillance nationally. The performance trends are consistent with those observed across the East and Southern Africa subregion, where country-level disparities highlight the importance of local-level capacity building and oversight [9].

The peer review was conducted to objectively assess variations in AFP surveillance performance across districts and to generate actionable insights through a structured, collaborative process. By engaging national and sub-national program staff as reviewers, the exercise allowed for direct observation, and verification of field practices, and critical reflection on district- and facility-level implementation gaps and strengths. The approach promoted cross-learning between high- and low-performing districts, encouraged professional accountability, and supported evidence-based recommendations tailored to context. This process provided a platform for practical problem-solving, ownership of surveillance improvement actions, and reinforcement of standard operating procedures through peer-to-peer dialogue. As Deressa et al. [10] discussed, understanding implementation processes is critical to informing program or system strengthening, including identifying implementation tools, strategies, and principles. As such, the review aimed to identify operational, structural, and contextual factors that enable or hinder surveillance performance to inform targeted corrective actions and strategic decision-making. Additionally, it aimed to facilitate cross-learning and collaboration among districts selected for the peer review and beyond. By combining field-level verification with peer-to-peer engagement, the exercise aimed to provide valuable insights into critical gaps to be addressed and best practices to be capitalized on in case detection, notification and investigation, stool specimen collection and transportation, and active case searches, while also documenting good practices that can be replicated across the districts to strengthen AFP surveillance quality and sensitivity.

Methods     

The peer review was designed as an operational evaluation using a mixed method approach, combining analysis of AFP surveillance indicators with field based qualitative assessment to establish actionable insights. We adopted the three UNEG principles: 1) Independence of evaluations and evaluation system(s); 2) Credibility of evaluations; 3) Utility of evaluations - [11] and followed the WHO/GPEI AFP surveillance quality threshold [8] for planning and implementation of the peer review, and reporting of the results.

Sampling frame: the sampling frame consisted of all 11 provinces, 63 districts and facilities from the selected districts.

Sampling process and sample selection: purposive and convenient sampling were used for sample districts. A total of 12 districts (6 high-performing and 6 low-performing), shown in Table 1 below, were selected based on key AFP surveillance indicators and other programmatic and geographic factors.

District level-low performing: an analysis of the district performance on NPAFP rate in 2022 and 2023 and number of AFP cases reported from January to May 2024 was conducted. There were 16 low-performing districts from 5 provinces (Manicaland, Mash Central, Mash west, Masvingo, Mat North) identified. From the 16, the least performing district was selected from each of the 5 provinces that had low performing districts. We added Mt Darwin district from Mashonaland Central Province because the province is least performing and borders with Mozambique.

District level-high performing: forty-seven (47) districts were identified as high-performing using the same criteria for low-performing districts. Harare, Chitungwiza and Bulawayo Urban districts /cities were selected because of the population density and high risk of polio emergence. The remaining 3 districts were selected from 3 remaining provinces (Matabeleland South, Midlands and Mashonaland East) so that each province was represented in the peer review.

Health facilities level: a total of 33 health facilities (three health facilities per district) were selected from both high and low-performing districts. The outcome of the selection, in terms of surveillance of priority sites, was 14 high, 10 medium and 9 low priority sites were identified.

Data collection: cata collection methods included key informant interviews at provincial, district and health facility level, interview of caregivers of reported AFP cases using AFP case verification form. The data collection was conducted using an ODK-based questionnaire following the process shown in Figure 1. Document reviews, including retrospective data review of registers (OPD, IMNCI, Rehab) at health facility level for the past 7 months were conducted guided by standard questionnaire guiding, verification of AFP line-lists, spot maps at all levels, review of RDNS, DHIS2 data for timeliness and completeness of reporting and review of feedback mechanisms. History taking and physical examination of AFP cases that were reported in the last 3 years were conducted to verify AFP cases and the quality of stool specimen collection, storage and transportation. Peer learning through the pairing of community health nurses (surveillance focal persons) from high and low performing districts was coordinated and facilitated to understand the primary focuses in the two categorical groups of districts.

Results     

All 11 provinces in the country were visited. Twelve districts (6 high performing and 6 poor performing) were visited. A total of 33 health facilities were assessed. Of the 33 health facilities visited, 14 were high priority, 10 were medium and 9 were low priority sites for AFP surveillance. Fifty-six surveillance focal persons at provincial, district and facilities were interviewed and thirty-four (34) AFP cases were identified for verification. A total of 56 questionnaires were administered (11 provincial, 12 districts and 33 facility level), and 24 case verification forms were completed, and 24 AFP cases were physically examined.

Key review findings

The key findings are summarized in Table 2.

Drivers of good performance

Strong surveillance systems

Clear lines of communication within the overall system from national to facility level. Structured reporting: a well-established surveillance system from community, health facility to provincial levels with weekly IDSR reporting and eHR implementation was noted to enhance overall surveillance performance. Documentation and filing: organized filing systems (by year, and disease) at all levels ensured traceability and accountability. Trained focal persons: trained and knowledgeable surveillance focal persons are more able to detect, investigate and report cases accurately. Active case search: conducting and documenting active case searches regularly according to priority level was found to enhance early case detection in high-performing districts. Community linkages: resence and collaboration with Village Health Workers (VHWs), Health Centre Committees (HCCs), and partner-supported outreach programs (e.g., UNICEF, Cordaid) was stronger in high-performing districts and HFs.

Strong routine immunization (RI) and surveillance synergy

Cold chain reliability: facilities with functional solar-driven refrigerators ensured vaccine integrity and readily available ice packs and vaccine carriers for stool storage and transportation. Active partners engagement: facilitated integrated outreaches funded by partners, (e.g., Higher Life Foundation), expanded service delivery, transporting stool specimen and logistical materials, implementing partners integrating surveillance activities into routine activities (ZACH). Community-based surveillance trainings, monitoring of community surveillance (ZACH). Quality and coverage of microplanning to address issues of inequity and facility community surveillance efforts.

Innovative practices

Community engagement: matabeleland North province facilities with community surveillance committees were stronger in community reporting of VPDs. Establishment of health facility committees comprising of traditional, religious leaders and school coordinators at community level through use of health centre committees on community-based surveillance. Technology use: whatsApp platform for feedback, reporting and communication and coordination at all levels; ODK-based active case search documentation and reporting. Creation and use of standard management tool to monitor and document active case search by surveillance officer (e.g., Mangwe district). Providing support for transportation care (food and accommodation) of AFP cases and caregivers at health facility for sample collection, ensuring high-quality sample collection and storage. (e.g., Shurugwi district). Facilities established partnerships with the business community to freeze ice packs need for sample storage and transportation under reverse cold chain.

Feedback, accountability and oversight

Complete and timely feedback on AFP case to health facility and caregivers motivate surveillance focal points and strengthen community trust (86% 13/15 % of facilities in high performing districts received timely feedback on AFP results). Documented monthly feedback on surveillance activities including challenges and best practices to all levels (national to province, province to district, district to facility, facility to community). Fourty four percent (44%) of the facilities in the low-performing districts did not receive such feedback. Recognition and appreciation of community health workers reporting AFP cases. Considerable number of facilities in good performing districts established strong community partnerships through recognition and appreciation of community health workers who reported AFP cases. This is done through documentation of their contribution and publicly announcing during monthly meetings.

Monitoring and supervision

Clear structure and tools for monitoring and supervision. Knowledge and capacity of monitors. Availability and standardization of monitoring and supervision tools. Enabling factors for monitors (logistics, incentives). Documentation and reporting of findings from monitoring activities and use for corrective action. Structured on-the-job training during monitoring activities. Availability of surveillance guidelines and SOPs at all levels. Consistent active search/integrates support supervision visits to all priority sites.

Drivers of low performance

Weak supervision and support

Minimal and infrequent visits to health facilities by the surveillance focal person (community health nurse)- Generally, there was low active case search in all priority sites, particularly in the low-performing districts. Six facilities in low-performing districts were not visited. Out of the expected 294 visits in supported health facilities during the 7 months in a low-performing district, only 45 (15%) visits were conducted. Poor documentation: no evidence of follow-up actions for late reporting or defaulter tracking (e.g., no listed children for follow-up). Inadequate AFP case verification: out of 77 AFP cases reported in the 7 months preceding the peer review 24 cases were checked by the review team. All of them were not verified by the district surveillance officers and 7/24 were found not to be true AFP cases.

Resource and process gaps

Not following standard operating procedures (time lapse between sample collection and start of reverse cold chain) (this was an observation not documented in ODK) number of caregivers reported stool samples were collected at home and brought to health facility outside vaccine career; Collection of single stool sample by care givers and health workers dividing into two samples and reporting as two separate sample collected on different days. Unavailability of specimen collection kits: 5/33 facilities lacked stool kits (3 from low-performing districts), delaying specimen collection. Cold chain failures: reverse cold chain not observed (e.g., Tsholotsho/Chitungwiza districts, contributing to low NPENT (6% vs. 10% target). Delays in specimen transportation from remote facilities to the district.

Knowledge and capacity issues

Staff turnover: new staff in 5 facilities lacked training, leading to gaps in AFP case definition knowledge. Lack of regular refresher training.

Inadequate community engagement

Lack of feedback: 16/33 facilities did not provide feedback to communities of which 10/33 are from low-performing sites, reducing caregiver trust and case reporting. Underused Committees: VHWs and HCCs existed but were rarely involved in defaulter tracing or AFP surveillance since documented evidence of their participation in AFP surveillance and defaulter tracing was not available in most facilities. No documentation of AFP cases reported by community health workers. Identification and training of key informants not yet done in all districts.

Discussion     

This peer review of AFP surveillance performance across selected high- and low-performing districts in Zimbabwe revealed distinct drivers of success and underperformance, offering valuable lessons for program improvement.

Well-structured surveillance systems as a foundation for high performance

High-performing districts benefited from established surveillance network that extended from Community Health Workers to National level Surveillance Focal Point. These systems were supported by routine Integrated Disease Surveillance and Response (IDSR) reporting and, in several instances, the implementation of electronic health records (eHR). The peer review identified consistently trained and knowledgeable surveillance focal persons, structured documentation practices (by year, district, and disease), and regular active case searches using standardized tools (e.g., T12, IMCI registers). Community linkages, especially through Village Health Workers (VHWs), Health Centre Committees (HCCs), and partner-supported outreach, played a key role in early detection and community-based surveillance. These findings are consistent with findings by Muzondo et al. [12] in Mwenezi district, Masvingo Province in Zimbabwe, where AFP surveillance knowledge level of health workers was good.

Well-structured surveillance systems as a foundation for high performance

High-performing districts benefited from established surveillance network that extended from Community Health Workers to National level Surveillance Focal Point. These systems were supported by routine Integrated Disease Surveillance and Response (IDSR) reporting and, in several instances, the implementation of electronic health records (eHR). The peer review identified consistently trained and knowledgeable surveillance focal persons, structured documentation practices (by year, district, and disease), and regular active case searches using standardized tools (e.g., T12, IMCI registers). Community linkages, especially through Village Health Workers (VHWs), Health Centre Committees (HCCs), and partner-supported outreach, played a key role in early detection and community-based surveillance. These findings are consistent with findings by Muzondo et al. [12] in Mwenezi district, Masvingo Province in Zimbabwe, where AFP surveillance knowledge level of health workers was good.

In contrast, low-performing districts lacked routine surveillance meetings, demonstrated weaker documentation practices, and had focal persons with limited knowledge. Missed or delayed AFP case identification was often linked to inadequate history-taking and failure to apply standard case definitions. Makoni et al. [13] found similar findings in Gokwe North district, where some health workers had limited knowledge of the AFP surveillance system. This lack of knowledge particularly for surveillance focal persons may result in missed AFP cases.

Synergistic immunization and surveillance activities enhanced detection

High-performing districts demonstrated effective integration between RI and AFP surveillance. Functional cold chain infrastructure, particularly solar-driven refrigerators, ensured proper storage of stool specimen and transportation under reverse cold chain. Partner support (e.g., Higher Life Foundation, ZACH, UNICEF) enabled integrated outreaches that combined vaccination, specimen transport, and community surveillance. Microplanning efforts also appeared to be more inclusive and targeted, addressing inequities in access and linking community-level surveillance to service delivery. Low-performing districts experienced cold chain failures, delays in specimen transport, and frequent unavailability of stool specimen collection kits. These logistical gaps not only compromised surveillance but also affected timeliness and completeness of response. Walker et al [14] found similar challenges in Kenya where inadequate financial resources for key elements of surveillance infrastructure, including active case searches, specimen transportation were reported. Addressing these gaps will be critical for improving the AFP surveillance system in Zimbabwe.

Grassroots-level innovation and ownership strengthen surveillance

In Matabeleland North community-level surveillance committees headed by village heads contributed to early detection and reporting of AFP cases. Districts leveraged technology (e.g., WhatsApp and ODK) to facilitate real-time reporting and coordination. Engagement with religious and traditional leaders, as well as informal dialogues with vaccine-hesitant caregivers, further enhanced community trust and responsiveness.

Zaka District has a robust community-based initiative called "Bereka Mwana", a Shona phrase translates to "carry the child," which is an initiative encouraging caregivers to bring their children along whenever they visit any health facility facilitating timely vaccinations and health services. It is a community-driven approach in EPI that has yielded high immunization coverage, and it can be adopted for community surveillance.

Conversely, low-performing districts underutilized such existing community structures and initiatives. Although VHWs and HCCs were present, there was little documented involvement in AFP case reporting or defaulter tracking. Key informants were not systematically identified or trained, and community feedback mechanisms were largely absent. As Chia et al. [15] argue, it is critical to have “innovative strategies aimed at reinforcing surveillance capacity and facilitating timely reporting of polioviruses”. There is also similar argument by Manyanga et al. [9].

Feedback loops and accountability mechanisms were critical enablers

In high-performing districts, feedback mechanisms were routine and systematic. Facilities received results of AFP case investigations, often accompanied by formal documentation and follow-up actions. In some instances, monthly feedback summaries were shared. Community health workers were recognized for their contributions, reinforcing motivation and engagement. The lack of feedback in low-performing districts negatively affected accountability. Most facilities were not receiving feedback and were failed to provide feedback to caregivers or communities, which may have undermined trust and reduced community-level reporting of suspected AFP cases. Deressa et al. [10] reported similar findings in DRC and Ethiopia where the lack of accountability mechanisms to inform individual performance was reported.

Monitoring and supportive supervision defined the operational pulse of the AFP surveillance system

Strong monitoring and supervision structures distinguished high-performing districts. Regular, well-documented visits were conducted using standardized tools, and surveillance guidelines and SOPs were available. Monitors had the necessary logistical support and used field visits to conduct on-the-job training and initiate corrective actions. Low-performing districts showed significant supervision gaps. In the six districts reviewed, only 24 visits were recorded across 8 facilities over seven months, well below the national expectations for site prioritization. Supervision was not only infrequent but also of poor quality, lacking documentation and follow-through. The absence of structured verification contributed to a high proportion of cases that were retrospectively deemed non-AFP. Similar findings were reported by Walker et al. [14], in Kenya, where among health facilities, only 44% had received planned quarterly supportive supervision from the district in the preceding 12 months, and 32% health facilities had written supervisor feedback to ensure identified gaps were addressed.

Procedural breaches and capacity gaps weakened low-performing districts

Number of deviations from standard procedures were documented in low-performing districts. These included incorrect stool sample collection and storage, reverse cold chain failures, and attempts to fabricate stool sample timelines by splitting a single sample. Five out of 33 facilities lacked stool collection kits, contributing to missed or delayed reporting. Furthermore, staff turnover and lack of refresher training resulted in inconsistent application of AFP case definitions and poor surveillance quality. This finding is consistent with what Makoni et al. [13] reported where the lack of knowledge of the surveillance focal points on the critical AFP surveillance procedures resulted in low surveillance performance in Gokwe North district, Zimbabwe. Madamombe et al. [16] also found similar gap in the study on the epidemic-prone disease surveillance system in Zimbabwe suggesting a critical need for targeted capacity building on surveillance in Zimbabwe and ensuring compliance to established protocols.

Limitations: the peer review did not include central hospitals which may limit generalizability of the findings in the country. Additionally, the peer review was constrained by time limitation and competing programs affecting thoroughness of the review. The peer review also relied on retrospective data spanning 2 years which may have resulted in recall bias affecting the accuracy and reliability of the information collected.

Conclusion     

High-performing districts thrive on well-supervised systems, strong routine immunization and surveillance synergy, innovative practices such as use of WhatsApp for feedback, community engagement, and optimum use of local resources for logistics and cold chain. In contrast, poor-performing districts had weak supervision, inadequate training, resource gaps and inadequate community engagement. Addressing these gaps will improve Zimbabwe's AFP surveillance system, ultimately contributing to the country's outbreak response and regional and global polio eradication goals. Our study provided critical recommendations given in Table 3 that, if implemented adequately, could strengthen the AFP surveillance system in Zimbabwe at all levels.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Maxwell Rupfutse, Wondu Asefa Gebresilasie, Amen Gumbo, Florence Shirehwa, Nomore Nyengerai, Mary Munyoro, Joan Marembo, and Alex Mafuzhe, participated in conceptualizing the study protocol and field data collection, constructed the study analysis, developed the background information, interpreted the data for academic reporting, and wrote the manuscript. All authors read and approved the final manuscript.

Acknowledgments     

We acknowledge the Ministry of Health and Child Care-EPI Unit Team from national to facility level, caregivers of the AFP case children, the WHO, UNICEF, BMGF, and IQVIA surge consultants for their contribution to the overall peer review processes.

Tables and figures     

Table 1: lists of systematically selected high- and low-performing districts in Zimbabwe based on AFP surveillance performance: retrospective review of 2023-2024 data

Table 2: common gaps and strengths identified during peer review of AFP surveillance at district level, Zimbabwe

Table 3: summary of key recommendations at national, province, district, health facility and community levels from AFP surveillance peer review, Zimbabwe

Figure 1: ODK-based data collection process for AFP surveillance peer review, Zimbabwe

References