Safeguarding Mongolia’s polio-free future: WHO initiates review of acute flaccid paralysis surveillance in a changing global risk environment

Sustaining vigilance after 25 years without polio

For more than two decades, Mongolia has safeguarded children from poliomyelitis through sustained immunization and public health vigilance. Since the country reported its last confirmed wild poliovirus case in 1999, no additional wild poliovirus has been detected, placing Mongolia among countries that have successfully maintained polio-free status for a generation.

This achievement represents more than the absence of disease. It reflects long-term commitment to government, strong routine immunization services, and close technical collaboration between national institutions and health partners. For a country with vast geography, dispersed population, and harsh seasonal conditions, maintaining this status has required continuous effort across all levels of the health system.

Yet global eradication remains unfinished. Wild poliovirus continues to circulate in Afghanistan and Pakistan, meaning that all countries remain vulnerable to importation until global transmission is fully interrupted. At the same time, circulating vaccine-derived polioviruses – particularly type 2 – have emerged as a major international concern, especially where immunity gaps allow transmission to persist.

For countries such as Mongolia, this changing epidemiological context means that protecting polio-free status depends not only on high vaccination coverage, but also on maintaining surveillance systems sensitive enough to detect even a single suspected case rapidly and respond immediately.

Acute Flaccid Paralysis (AFP) surveillance remains the global gold standard for detecting poliovirus transmission. Every suspected AFP case in a child under 15 years of age serves as a critical alert for possible poliovirus circulation and must be investigated without delay.

Recognizing this responsibility, Mongolia with support from the World Health Organization (WHO), initiated a rapid AFP surveillance review to examine whether its current surveillance system remains sufficiently sensitive, responsive, and aligned with evolving certification requirements for both wild poliovirus and vaccine-derived polioviruses.

Checking patient records for potential AFP cases. © WHO Mongolia

Assessing surveillance where it matters most

The review was conducted from 3 to 9 December 2025 across multiple levels of the health system, covering provincial health departments, district health centers, soum-level facilities, private providers, and tertiary referral hospitals in Ulaanbaatar, Khuvsgul Province, and Orkhon Province.

The assessment aimed to move beyond routine indicator review and examine how surveillance operates in practice: whether clinicians recognize AFP, whether reporting pathways function efficiently, whether records capture missed opportunities, and whether surveillance remains sensitive enough in areas where no cases have been reported for several years.

Interviews with surveillance focal points, epidemiologists, clinicians, and records staff revealed that the essential surveillance framework remains in place. Reporting channels through the early warning system continue to function, focal persons are designated at provincial and district levels, and communicable disease reporting remains active across much of the country.

Over time, some AFP‑specific surveillance functions have faced implementation challenges. In several locations, reporting has largely depended on passive notification through the early warning system, with limited application of routine weekly zero reporting and variable prioritization of high‑risk reporting sites. Supportive supervision opportunities have also been constrained. In addition, key surveillance performance indicators – such as the non‑polio AFP rate, stool adequacy, and timeliness – were not consistently reviewed at subnational level, which may have limited the use of surveillance data for local performance monitoring and improvement.

This gradual reduction in AFP-specific attention is understandable in a setting where no confirmed polio cases have occurred for many years. Yet paradoxically, the absence of visible disease increases the need for stronger surveillance sensitivity. A system that reports no cases must still demonstrate that it is actively capable of finding them.

Reviewing AFP surveillance performance at facility level. © WHO Mongolia

Challenges

Several challenges were identified through a retrospective review of medical records at national and subnational levels. This review indicated that some children under 15 years of age with diagnostic profiles suggestive of AFP were not formally notified through the surveillance system. These observations do not suggest a lack of engagement or commitment among clinicians; rather, they highlight the importance of ensuring that AFP surveillance procedures are consistently embedded within routine clinical workflows. Where clinicians focus primarily on diagnosis and immediate treatment, AFP reporting may be unintentionally deprioritized unless supported by simple prompts, regular reminders, and clearly defined responsibilities.

At the same time, these findings point to one of Mongolia’s strongest opportunities: large referral hospitals are already managing the cases most relevant to AFP detection, and with stronger integration into surveillance processes, these institutions are well positioned to serve as a central pillar for enhancing surveillance sensitivity nationwide.

The review also noted practical challenges affecting AFP surveillance in remote settings, where health workers manage many responsibilities alongside routine reporting. The move to electronic systems has improved overall reporting but has, in some cases, made AFP less visible without clear prompts in clinical workflows. Limited availability of guidance materials and specimen collection tools have occasionally delayed investigation despite clinical awareness. Health workers consistently expressed strong interest in strengthening surveillance when supported with practical tools, refresher training, and clear expectations. Engagement with private providers further showed that valuable expertise already exists beyond the public system, offering an opportunity to strengthen surveillance through broader collaboration.

Turning findings into action

Immediate actions focus on strengthening the reporting network by formally engaging major hospitals, private providers, and priority facilities; ensuring the availability of stool collection kits and job aids; introducing mandatory AFP zero‑reporting functions within electronic systems; and rapidly orienting newly assigned staff.

Short‑term priorities include updating national AFP guidelines, developing online learning modules to address staff turnover, incorporating AFP surveillance into annual workplans, conducting active surveillance visits to high‑priority facilities, strengthening specimen transport procedures, and providing regular feedback through surveillance bulletins and data review meetings.

Longer‑term priorities focus on sustainability and include holding annual national AFP workshops, conducting provincial refresher training, expanding environmental surveillance, undertaking periodic internal and external reviews, and gradually transitioning toward stronger domestic financing.

Integrating AFP surveillance into annual operational plans, allocating dedicated resources, and establishing multi‑year sustainability strategies will be essential to maintaining readiness under both wild poliovirus and vaccine‑derived poliovirus certification requirements.

The review team engages with district EPI team. © WHO Mongolia

Sustaining polio‑free status through strong and sensitive surveillance

Sustaining effective AFP surveillance requires shared awareness and consistent participation across the health system. Clinicians play a critical role in recognizing AFP as a reportable condition, while reporting units contribute through timely notification, investigation, specimen collection, and use of surveillance indicators to guide action.

After more than 25 years without polio, Mongolia’s next public health milestone goes beyond maintaining the absence of disease. It lies in demonstrating that vigilance remains strong enough to detect even the rarest signal, respond promptly, and protect future generations, while continuing to contribute meaningfully to the final stage of global polio eradication.