At the beginning of this year, there was a thrum of excitement among global health experts: Eradication of polio, a centuries-old foe that has paralysed legions of children around the globe, seemed tantalisingly close.
Pakistan, one of only two countries where wild poliovirus still circulates, had not recorded cases in more than a year. Afghanistan had reported only four.
But eradication is an uncompromising goal. The virus must disappear from every part of the world and stay gone, regardless of wars, political disinterest, funding gaps or conspiracy theories. New signs of the virus in a single country can derail the effort.
In polio’s case, there were several ominous setbacks.
Malawi in February announced its first case in 30 years, a 3-year-old girl who became paralysed after infection with a virus that appeared to be from Pakistan. Pakistan itself went on to report 14 cases, eight of them in a single month last spring.
In March, Israel reported its first case since 1988. Then, in June, British authorities declared an “incident of national concern” when they discovered the virus in sewage. By the time New York City detected the virus in wastewater last week, polio eradication seemed as elusive as ever.
“It’s a poignant and stark reminder that polio-free countries are not really polio-risk free,” said Dr Ananda Bandyopadhyay, deputy director for polio at the Bill Melinda Gates Foundation, the largest supporter of polio eradication efforts.
The virus is always “a plane ride away,” he added.
Polio is a highly contagious and sometimes deadly enemy, capable of ravaging the nervous system and causing paralysis within hours. Those who recover could relapse and become seriously ill years later.
The virus multiplies in the intestine for weeks and could spread through feces or contaminated food or water — for example, when an infected child uses the toilet, neglects washing hands and then touches food.
For decades, the virus terrorised families, causing paralysis among more than 15,000 American children each year and hundreds of thousands more worldwide. Its retreat is a triumph of vaccination. After the first vaccine arrived in 1955, the number of cases dropped precipitously, and by 1979, the United States was declared polio-free.
Although the United States and Britain have high immunisation rates, they also have pockets of low immunity that allow the virus to flourish. In those communities, all unvaccinated people — not just children — are at risk. If polio continues to spread in the United States for a year, the country may lose its polio-free status under World Health Organization guidelines.
Aid organisations first aspired to eradicate polio in 1988 and poured billions of dollars into the Global Polio Eradication Initiative, a consortium of six partners, including the Gates Foundation, WHO, and Centers for Disease Control and Prevention.
Despite the recent cases, the progress is unmistakable: Global cases of polio have fallen by 99 per cent — from 350,000 cases of paralysis in 1988 to about 240 so far this year.
That success “is both a miraculous thing and a thing that’s taken way, way longer than people expected,” Bill Gates, who has taken a pointed interest in polio, said in an interview in February. “Eradications are super hard, and they rarely should be undertaken.”
Ending polio has been particularly challenging.
There are three strains of the wild poliovirus. Type 2 was declared eradicated in 2015, and Type 3 in 2019. Only Type 1 poliovirus remains at large, and only in Pakistan and Afghanistan.
Immunisation for polio can be done in one of two ways. The injected vaccine used in the United States and most rich countries contains killed virus, is powerfully protective against illness but doesn’t prevent the vaccinated from spreading the virus to others.
Mass vaccination campaigns rely on the oral polio vaccine, which delivers weakened virus in just a few drops on the tongue. The oral vaccine is inexpensive, easy to administer and can prevent infected people from spreading the virus to others, a method better suited to extinguishing outbreaks. — The New York Times
Apoorva Mandavilli
The writer is an American investigative journalist whose work has focused on medical science
