Polio Is Still a Threat in South Asia

GENEVA – Despite the overwhelmingly good news from the World Health Organization (WHO) that two of the three wild polio virus strains have been eradicated, healthcare workers have been unable to eliminate the disease in Pakistan and Afghanistan. Recent outbreaks of polio in the Philippines is also under investigation. However, the continuing presence of the virus in South Asia is the primary area of concern.

The WHO certified that wild poliovirus type 2 was eradicated in 2015.

Polio outbreaks will continue to be a concern in cases where children are not being vaccinated. This is the case in Afghanistan and Pakistan.

October 24 is World Polio Day. Professor David Salisbury, chair of the independent Global Commission for the Certification of Poliomyelitis Eradication, presented the official certificate of WPV3 eradication at WHO headquarters in Geneva.

“Wild poliovirus type 3 is globally eradicated,” said Professor Salisbury.  “This is a significant achievement that should reinvigorate the eradication process and provides motivation for the final step – the eradication of wild poliovirus type 1. This virus remains in circulation in just two countries: Afghanistan and Pakistan.”

Outbreaks will continue to be a concern in cases where children are not being vaccinated. This is the case in Afghanistan and Pakistan. Failure to protect is common in places that experience population movement, insecurity, or cultural resistance.

Afghanistan and Pakistan presented 88 cases of wild polio virus infection in the past year. Officials remain confident that, as long as eradication efforts are not abandoned, success could be on the horizon. Walter Orenstein, associate director of the Emory Vaccine Center, emphasized the need to keep working toward complete eradication.

“Abandoning the effort now will not keep things at the current level. We will get a major resurgence. And that’s what we need to explain to people: Don’t think if you stop, it will be over. It will not be over, and it will get a lot worse.”

Officials remain concerned about the spread of vaccine-derived polio.

The wild strains are those surviving on their own in natural settings conducive to the growth of the virus.

Vaccine-derived polio is typically spread in unsanitary areas, particularly those where open defecation is practiced or where toilet facilities are not maintained in a hygienic condition.

According to WHO, “When a child is immunized with OPV, the weakened vaccine-virus replicates in the intestine for a limited period, thereby developing immunity by building up antibodies. During this time, the vaccine-virus is also excreted. In areas of inadequate sanitation, this excreted vaccine-virus can spread in the immediate community . . . before eventually dying out.”

If the community is under-immunized, the excreted vaccine-virus can subsist and circulate for quite some time. The longer it survives, the more dangerous it can become as it genetically self- modifies.

Under-immunized communities or large populations are particularly susceptible to both wild poliovirus and vaccine-derived virus.

Pakistan has begun a targeted approach of vaccination, hoping to ensure that every child is vaccinated.

The campaign to eradicate polio is made more difficult by polio-outbreaks in areas that had previously been polio-free. When officials respond to an outbreak, they are forced to use resources that are needed to successfully complete their work in Afghanistan and Pakistan where the disease is endemic.

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