Hidden Polio in Healthy Kids: What It Means for Public Health

Silent Polio Cases Found in Papua New Guinea
Kids sitting on a bench
In 2023, the Global Polio Eradication Initiative (GPEI) reported 1,164 cases of circulating vaccine-derived poliovirus (cVDPV) globally, up from 674 cases in 2022. These cases occurred in over 30 countries, mostly in Africa and Asia.(Representational Image: Unsplash)
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On 9 May 2025, a surprising news from Papua New Guinea's health authorities: a type of poliovirus, circulating vaccine-derived poliovirus type 2 (cVDPV2), was detected in stool samples taken from two healthy children in La City, Morobe province. The news comes following the detection in April of environmental samples, which already indicated the virus's presence.

The kids were asymptomatic, yet the virus was circulating in their systems. This asymptomatic spread is now giving rise to concern, especially in a region where polio vaccine coverage is frighteningly low.

What is vaccine-derived poliovirus?
OPV is produced using a weakened strain of the poliovirus, which is designed to create immunity. At times, in areas with low rates of vaccine coverage, the weakened virus may continue to spread long-term and develop. If it develops enough, it will behave like wild poliovirus and cause disease. The developed form of the virus is referred to as vaccine-derived poliovirus.

Why the Virus Found in Healthy Kids Is a Red Flag

While children are healthy and not ill, the virus they harbor is a public health risk. It means cVDPV2 is quietly circulating within the community, potentially infecting other people who are unvaccinated or under-vaccinated.

Morobe province had as low as 44% third-dose oral polio vaccine (OPV3) coverage in 2024, far from the threshold required for effective herd immunity.

Disabled woman in wheelchair with daughter.
The Philippines Outbreak (2019–2020) had its first reemergence of polio in 19 years. Resulted in 16 confirmed cases of VDPV, which triggered a massive national immunization campaignRepresentative image: Freepik

How does polio spread without displaying symptoms?

Here comes the catch: Polio is often symptom-free. In fact, 70% of polio infections are totally asymptomatic. People don't feel a thing but can still shed the virus from their stool and transmit it unknowingly, particularly in unsanitary places.

Some 1 in 4 infected individuals might have mild symptoms like:

  • Fever

  • Sore throat

  • Headache

  • Upset stomach

  • Fatigue

These flu-like symptoms tend to clear in a matter of days and are rarely ever associated with polio unless they are tested properly.

But in rare but severe situations, the virus invades the nervous system and results in:

  • Neck pain (spinal cord and brain meningitis)

  • Paresthesia (limb tingling)

  • Paralysis

  • Delayed-onset complications such as post-polio syndrome, years after the initial infection

What needs to be done now?

The finding of cVDPV2 in asymptomatic children is an eye-opener. Highlights the need for:

  • Increased vaccination in high-risk communities

  • Improved surveillance to detect silent transmission early

  • Increased public awareness of the importance of vaccination

A single unvaccinated child in a low-coverage community can be the breeding ground for an outbreak. Persistence in vaccination, education, and surveillance is the key to preventing polio.

(Input from various sources)

(Rehash/Muhammad Faisal Arshad/MSM)

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