As Yogi Berra (or Niels Bohr or Samuel Goldwyn) is supposed to have said, it’s difficult to make predictions, especially about the future. It’s especially dangerous to try to predict the behavior of infectious diseases, when small unpredictabilities in climate or trade or the behavior of governments can bring a problem that we thought was handled roaring back to life.
But as 2016 opens, it is fair to say that the disease public health experts are pinning their hopes on, the one that might truly be handled this year, is polio. There were fewer cases last year than ever in history: 70 wild-type cases, and 26 cases caused by mutation in the weakened virus that makes up one of the vaccines, compared to 341 wild-type infections and 51 vaccine-derived ones the year before. Moreover, those wild natural infections were in just two countries, Afghanistan and Pakistan, and the vaccine-derived cases were in five. The noose is tightening.
The most that health authorities can hope for this year is to end transmission of polio. The ultimate goal is eradication, which has happened only twice—for one human disease, smallpox, and one animal one, rinderpest. To declare a disease eradicated requires that the entire world go three years without a case being recorded. If there are no polio cases in 2016, eradication might be achieved by the end of 2018.
Which would make for nice round numbers, because the polio eradication campaign began in 1988. It is safe to say that no one expected it would take anywhere near this long; the smallpox eradication campaign, which inspired the polio effort, reached its goal in 15 years.
Smallpox was declared eradicated in 1980, so long ago that most people have no knowledge of how devastating a disease it was, or even what a case of the disease looked like. (There are survivors left, but they are aging; the last person infected in the wild, Ali Maow Maalin of Somalia, died in 2013.) In the same way, we’ve forgotten how difficult it is to conduct an eradication campaign. Smallpox was the first campaign that succeeded, but it was the fifth onethe fifth onethe fifth one that global authorities attempted. In its success, it demonstrated what any future campaign would need: not just a vaccine that civilians could administer, but an easy-to-access lab network, granular surveillance, political support, huge numbers of volunteers, and lots and lots of money.
In its own trudge to the finish, the polio eradication campaign has stumbled over many of those, from local corruption to extremist opposition to the still almost unbelievable interference of the CIA (which I covered here and here), along with the virus’s own protean ability to cross borders (to China) and oceans (to Brazil).
But now, at last, the end does look in sight. I asked Carol Pandak, director of the Polio Plus program at Rotary International — which since 1988 has lent millions of volunteers and more than a billion dollars to the eradication campaign — how she thinks the next 12 months will go.
“We are getting closer,” she told me. “We have only two endemic countries left. Of the three types of the virus, type 2 was certified eradicated in September, and there have been no type 3 cases globally for three years. And Pakistan and Afghanistan have goals to interrupt transmission internally in May 2016.”
The diminishment of wild polio paradoxically creates greater vulnerability to vaccine-derived polio, which happens when the weakened live virus used in the oral vaccine mutates back to the virulence of the wild type. The only means of defusing that threat is to deploy the killed-virus injectable vaccine, which is widely used in the West but until recently was considered too expensive and complex to deliver in the global south.
To begin the transition, Pandak said, countries that still use the oral vaccine have agreed to give one dose of the injectable as part of routine childhood immunizations for other diseases. That should strengthen children’s’ immune reactions to polio, so that the reversion to wild type — which occurs as the weakened virus replicates in the gut — does not take place.
In the smallpox campaign, when eradicators thought they were almost done, there was a freak weather event—the worst floods that Bangladesh had experienced in 50 years—that triggered an internal migration and redistributed the disease. Polio is just as vulnerable to last-minute disruptions, especially since the two remaining endemic countries are hotspots of unpredictability. Travelers from Pakistan actually carried polio into Afghanistan in August.
“In Pakistan, the army has committed to providing protection for vaccinators in conflict areas,” Pandak told me, “and another strategy that has been successful has been to set up border posts to immunize people as they are fleeing areas of conflict and military operations. I have seen Rotary volunteers staffing 24/7 kiosks in train stations and toll booths, so that we can get people wherever they happen to be.”
There is no question that hurdles remain. By the World Health Organization’s order, polio is still considered a “public health emergency of international concern,” which requires countries where the disease is extant to either ensure its citizens are vaccinated before leaving, or prevent their crossing the border. And polio still lives quiescently in lab freezers all over the world, and those will have to be searched and their contents eliminated lest a lab accident bring the disease alive again (a warning that was recently circulated for rinderpest as well). Plus, up til now, the injectable vaccine has been made by starting with a virus that is not only live but virulent, posing the risk that a lab accident that could release it; British scientists announced on New Year’s Eve that they may have found a way to weaken it while still yielding a potent vaccine.
When it goes, if it does, polio will gift the world not only with its absence, but also with the abundant health infrastructure that was set up to contain and eliminate it, and can be turned to other uses. When I talked to Pandak, she sounded excited at the possibility that countries and volunteers would be able to turn their attention away from a single disease and toward ensuring the overall health of children.
“We have been doing this for 30 years,” she said. “We’ll continue to fundraise, advocate and raise awareness to the last case. We are committed to seeing this to the end.”