On October 24, 2019, World Polio Day, the World Health Organization (WHO) announced a “historic step” in conquering the childhood crippler polio. A panel of experts certified that the second of three types of virulent disease had been wiped off the face of the earth.
The last reported case of type 3 polio occurred in 2012 in Nigeria. A poliovirus is considered eradicated after three years with no new infections.
There are three types of polio. They all produce the same crippling symptoms – including paralysis and death – but spring from distinct viruses.
Now, the Global Commission for the Certification of Poliomyelitis Eradication claims that only wild poliovirus type 1 is still at large in the world. Type 2 was declared eradicated officially in 2015, followed by type 3 this week.
Type 1 poliovirus is still active in Pakistan and Afghanistan, with 88 people infected this year. That number popped up from the 22 recorded cases in 2017, the lowest global annual figure to date.
Poliomyelitis (polio) is transmitted from one person to another. The infection spreads mainly as a consequence of bad hygiene, through the fecal-oral route or, less often, by contaminated water or food. The virus multiplies in the intestine and invades the nervous system, causing irreversible paralysis, sometimes within hours, in one out of every 200 patients. Some patients die because they can’t breathe.
The first signs of polio, which is incurable, include:
- Stiffness in the neck
- Pain in the limbs
According to David Salisbury who chairs the independent Global Commission for the Certification of Poliomyelitis Eradication, the good news about type 3 polio is “a significant achievement that should reinvigorate the eradication process and provides motivation for the final step — the eradication of wild poliovirus type 1.”
A year ago, health officials hoped that polio could be wiped out by the end of 2018. At the time, only three countries – Pakistan, Afghanistan, and Nigeria – had not eradicated the highly contagious childhood disease. The number of cases had plunged over the past 30 years, down to 22 in 2017 from around 350,000 infections reported in 1988.
Michel Zaffran, director of polio eradication at the World Health Organization, stated:
“We are closer than we have ever been before to wiping out this virus. The next few months will tell us if we may be able to finish the job this year as this is the time when the virus is circulating. We may need another year.”
Polio infection can be prevented by vaccination. However, a mutated version of the oral type 2 vaccine (which has been phased out of use in 2016) can spread the virus. This derivative infection is distinct from the three “wild” virus types.
Vaccine-derived polio spreads when someone ingests the oral vaccine – which contains a living form of the weakened virus. The vaccination virus can live in the intestines long enough to be transmitted from person to person, further mutating as it spreads.
Zaffran explained why vaccine-derived polio is dangerous:
“When it circulates for a long time among too many poorly vaccinated or unvaccinated children, this is how it is allowed to mutate and become virulent again.”
The Global Polio Eradication Initiative administered 10 billion doses of oral polio vaccine globally between 2000 and 2011. Twenty outbreaks of vaccine-derived virus resulted in 580 cases of polio.
Cases of vaccine-derived polio can arise in populations where immunity is low and sanitation is poor. Those vaccinated can excrete the virus and put the unvaccinated at risk of infection.
Matshidiso Moeti, the WHO regional director for Africa, warned that the struggle to rid the world of polio is not over yet despite the recent victory vanquishing the second viral strain:
“The eradication of wild poliovirus type 3 is a major milestone towards a polio-free world, but we cannot relax.”
In September 2019, the Philippines unveiled plans to conduct an emergency vaccination campaign after re-emerging polio caused the first two recorded cases there in the past 20 years.
For the most part, polio strikes children younger than 5 years. During the mid-20th century, at its peak, polio was responsible for 500,000 deaths annually. More than 350,000 cases in 125 polio-endemic countries were counted in 1988, the year WHO launched its global polio eradication program.
Since 1988, reported cases of wild poliovirus have gone down by over 99 percent, according to WHO, to 94 this year.
Award-winning science writer Richard Conniff was optimistic about our chances for getting rid of the virulent childhood illness:
“India, where polio was paralyzing 500 to 1,000 children per day in the 1990s, eliminated the disease in 2014. The wrenching spectacle of child polio victims begging in that nation’s streets, with their twiglike legs folded beneath them, is now history.”
Conniff also lauded the achievements of persistent health workers who continue their work despite local opposition:
“Nigeria, where anti-government gunmen assassinated nine women polio vaccinators in 2013, has now gone three years without any evidence of wild poliovirus — and seven years without type 3 — largely through the heroic persistence of community health workers.”
If efforts to eradicate polio prove successful, it would be the second human disease to vanish from the globe, after smallpox was defeated in 1980.