The world is closer than ever to eradicating polio forever

 As Zerospinzone readers know, the eradication of polio has been the target of a massive international effort started in 1988 and led by the World Health Organization, the United Nations Children's Fund and the Rotary Foundation. The effort has been incredibly successful and in fact has pushed the deadly polio virus to the brink of extinction. So far this year there have only been 4 cases of poliomyelitis caused by the wild polio virus. As far as we know, the wild virus hangs by a thread in just two countries, Pakistan and Afghanistan.

Administering the oral polio vaccine

Credit: Michael Tsegaye, Flickr

However, the final eradication of the disease has been complicated by the fact that the weakened polio viruses used in the Oral Polio Vaccine occasionally mutate to a virulent, disease causing form. This kind of mutation is very rare, but with hundreds of millions of doses administered, in recent years there have been more cases of poliomyelitis caused by the mutated vaccine, especially the type 2 vaccine, than caused by the wild virus itself. (The polio virus comes in 3 varieties, each of which has its own vaccine. The type 1 and type 3 viruses appear to have been eradicated, and recent vaccine-derived cases have all come from the type 2 vaccine.

The good news is that researchers have developed a new type 2 oral vaccine--nOPV2--that is genetically much more stable than the earlier version, and so much less likely to mutate to a disease-causing form. The new vaccine successfully snuffed out a recent outbreak of vaccine-derived illness in Tajikistan without leading to any new cases. This successful use of the novel type 2 vaccine provides hope that the few countries where either wild polio virus or disease-causing forms of the older type 2 vaccine still exist can soon join the rest of the world and be certified as completely free of polio.

Then--hopefully very soon--polio will join smallpox as once dread and deadly human diseases that have been permanently wiped from the face of the earth. 

POLIO ERADICATION UPDATE 4-30-21

 As Zerospinzone followers know, I'm fascinated by the quest not just to control or cure deadly diseases, but to eradicate them completely. The scourge of smallpox was defeated in 1980, and we've been closing in on polio since the deployment of the first (Salk, inactivated virus) vaccine in 1954, country by country, continent by continent.

Polio has been with us for thousands of years

This depiction is from Egypt's 18th Dynasty--1403 to 1365 BC

Credit: Deutsches Grünes Kreuz

Today, the wild polio virus hangs on in just two countries, Pakistan and Afghanistan, with just one case reported in each of those countries so far this year. We may really be on the verge of totally eliminating the wild polio virus from Planet Earth.

Even when that remarkable feat has been accomplished, the battle won't be over. The oral polio vaccines that have been so incredibly successful have one flaw--the attenuated viruses they use very occasionally mutate back into disease-causing variants. So far this year there have been 73 cases in 10 countries, fewer than last year at this time, but still a serious problem. 

The Global Polio Eradication Initiative has developed and initiated a strategy or endgame to deal with this issue. They plan to gradually phase out the massive provision of attenuated oral vaccines, phase in the use of an inactivated-virus vaccine as needed, and, hopefully, bring the millennial reign of polio to an end.

I'll continue to report on their progress towards this grand goal.

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REA 4-30-21 

POLIO STRIKES BACK--ERADICATION ENDGAME SURPRISINGLY DIFFICULT

This has been a very mixed year for the global polio eradication campaign.

What the global polio eradication campaign

wants never to happen again

The good news is that two of the three strains of wild poliovirus have been conquered; they no longer exist except in laboratories.

The mixed news is that the remaining wild poliovirus only exists in two countries, Afghanistan and Pakistan. However, the number of cases in both countries, especially in Pakistan, has been higher than in 2018. The two countries suffered 125 cases of polio compared to just 33 last year, 101 of those in Pakistan. In both countries, strife, insecurity and anti-vacccination propaganda and rumors have enabled the virus to hold on.

The bad news is that the number of people--mostly children--sickened by poliovirus that has mutated back to a virulent form from the live-but-attenuated polio vaccine has more than doubled since 2018. This back-mutation only occurs in one person out of an estimated 2.8 million, but since 450 million children are getting the attenuated vaccine every year, a significant number of cases are inevitable as long as the oral vaccine remains in wide use--unless the surrounding population has a very high rate of "herd immunity." There were 241 such cases in 2019 vs. just 104 in 2018.

The solution is complex, but at hand. In part, it depends on the rapid release of an oral vaccine against the type 2 poliovirus, which is expected to be less likely to mutate to a virulent form. You can read about the global polio endgame strategy here. Plans and resources are in place to make this transition, and the intense, decades-long global campaign to wipe out this deadly disease once and for all will succeed, even if not quite as quickly as hoped.

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REA

WE'RE SO CLOSE TO ERADICATING POLIO

As followers of zerospinzone.blogspot.com know from previous posts, I'm enthralled by the goal of not just treating or curing diseases, but eradicating them entirely.

Among human diseases, smallpox was the first to be wiped away, with the last case of a natural infection by this once devastating scourge occurring in October, 1977.

Polio, a paralyzing and sometimes fatal disease that struck down more than 500,000 people per year, most of them children, as recently as the 1940s and '50s, will hopefully be the next to go. Starting with the development of the Salk inactivated virus vaccine in the early 1950s and the Sabin attenuated virus oral vaccine in the early 1960s, polio has been eradicated in country after country, continent after continent, through massive, sustained, costly and often extremely difficult public-health efforts.

 An infant receives the oral polio vaccine at a mobile clinic in Afghanistan, February 15, 2017

Credit: World Health Organization (WHO)/ S.Ramo

This enormous international effort has been incredibly successful. So far this year, only three cases of polio have been diagnosed worldwide, all in war-torn Afghanistan. In other words, the wild polio virus that once circulated freely throughout the world, has now been caged and almost completely destroyed, and now may hang on in just one small corner of one country.

It will still take intense surveillance and continued mass vaccination programs to strike the final blow against this deadly disease and ensure that it can not flare up anywhere every again.

But the world is so very close. What an accomplishment it will be.

REA

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QUICK UPDATE ON POLIO ERADICATION PROGRESS -- WE'RE SO CLOSE

Followers of this blog know that I'm fascinated by the international effort to eradicate polio. Wiping out this paralyzing, often deadly disease will be one of humankind's great accomplishments. The only other human disease that we've been able to eradicate is smallpox--the last spontaneous case was in 1977.

According to the Global Polio Eradication Initiative, the effort is incredibly close to success, with just 5 cases reported worldwide this year, to May 24 (vs. 16 this time last year). In the early 1950s, before the Salk and Sabin vaccines were introduced, 15,000 children died or were paralyzed by the poliovirus every year just in the United States, 500,000 worldwide.

It's taken decades of dedicated, sometimes dangerous work by scientists, international organizations, and on-the-ground health providers to reduce that number from 500,000 to 5. The goal now is to shrink it to zero.

It appears that the polio virus now survives in just a few locations--the 5 cases all occurred in Pakistan and Afghanistan, destabilized by war and refugees. In addition, all 5 cases were caused by Wild Polio Virus 1 (WPV1), meaning that the other two strains of wild polio virus, WPV 2 and 3, may already be eradicated.

Wild Polio Virus Type 3

Credit: Manuel Almagro Rivas/CreativeCommons

Massive vaccination programs of at-risk children and adults are continuing, and will need to to continue for some time even after there are no more documented cases.

We're so close . . .

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