Could the world see a resurgence of polio? Experts fear a cautionary tale in measles

Helen Branswell

As measles case counts have exploded around the globe this year, public health officials doggedly trying to rid the world of another disease scourge have watched the numbers rise with some concern.

That disease is polio, and for the people who have long worked to eradicate it, the resurgence of measles has become a cautionary tale — both useful and unsettling — of why the polio campaign must push on across the finish line. Failure to do so could have dire consequences.

“In my opinion, there’s no doubt if we stopped the extra efforts we do for polio, we’d have a big resurgence,” said Dr. Walter Orenstein, associate director of Emory University’s Vaccine Center and a consultant to the Global Polio Eradication Initiative.

The effort to eradicate polio is nearly two decades past its original target date for completion, and there are concerns about what could happen if funding dries up or the political will to persevere towards the elusive goal erodes.

Read more: The measles virus was down and out. Now it’s primed for a comeback

For now, wild poliovirus is cornered in eastern Afghanistan and western Pakistan, hard-to-access places where vaccination teams are often unwelcome and unsafe. But it is not magically corralled there. Any easing of the pressure on the virus could see a version of what is happening with measles unspool with polioviruses — though on a slower, less visible but still insidious basis.

The polio program, which goes by the acronym GPEI, has drawn up a five-year plan to take the effort through to the end of 2023; theoretically, with some lucky breaks, the job could be completed by then, Michel Zaffran, director of polio eradication at the World Health Organization, told STAT.

But the polio program is not known for lucky breaks — very much the opposite, in fact. Through massive efforts it has succeeded in battling paralytic polio cases down from about 350,000 cases a year when the effort began in 1988 to very low numbers; in 2017, the best year on record, there were only 22 reported cases of paralytic polio. But the following year, the virus rebounded, with 33 cases reported.

So far this year there have been 65 cases reported, with many of them coming during what should have been polio’s low season, when the virus typically doesn’t transmit well. “But the low season was not really low,” Zaffran said. (It’s currently high season for polio.)

The program needs to raise $3.27 billion to cover the costs it will incur between now and the end of 2023. Funders — a number of governments, the Bill and Melinda Gates Foundation, and the service organization Rotary International, which has been a partner in the eradication effort from the start and has raised $2 billion for the effort — are weary and worried. Zaffran hears it as he makes the case to funders.

“How long is it going to take? How much money is it going to cost? Is it worthwhile?” he said. “And basically their rationale is, ‘Well, can’t we control the disease in Pakistan and Afghanistan and stop investing such mass a massive amount of resources?'”

The answer, though, is no. It costs about $1 billion a year to keep polio transmission at the current levels. Relenting on that spending would see polio numbers climb again. Zaffran said though he hears the questions, the funders already know the answer.

“They’ve started an effort. They need to bring it to the end, however painful it is for this last mile,” he said.

Kimberly Thompson is a mathematical modeler who has been working on polio for years. In 2007, she published an analysis showing that even small decreases in the intensity of the polio eradication efforts would lead to large outbreaks of polio.

Thompson argued then for more investment in the polio program, saying the costs of not doing so would be greater in the long run. A dozen years later, Thompson makes the same argument.

“From a health economics perspective, the best thing to do is go big and go strong until you’re really done and then be done. You can’t take your foot off the gas and expect that you’re not going to lose ground,” said Thompson, who is president of the nonprofit Kid Risk, which conducts research on infectious diseases including polio. “If we’re not doing that and not willing to put in the resources then it takes longer and costs more. And this is what it looks like.”

What’s happening with measles serves as a reminder. Last week the WHO released preliminary data for 2019 that showed huge increases across the world, attributable to declines in vaccination rates. Case numbers for the African region are up 900%; in WHO’s western Pacific region, cases are up 230%. The United States has recorded more measles than the country has seen in a quarter century. Numbers in Europe have already exceeded the tally for all of last year.

The measles virus is highly contagious and the illness it causes is generally visible, with its bright red rash. Polio is not as easy to spot, which would create major problems were it to spread globally again.

Read more: With a surge in cases of mysterious polio-like condition, CDC appeals to doctors to help crack case

Nearly three-quarters of infections — 72% — have no symptoms and in another 24% of cases children have non-specific illness, nothing that would signal polio to a parent or a health care provider. In fact, less than 1% of children infected will develop paralytic polio.

“Polio is a little more stealth in its ability to move around the world,” said Dr. William Moss, executive director of the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health. “Most infected persons are asymptomatic. And people can shed polioviruses for months. So you have a great opportunity for infected individuals to travel. If they end up in a community where there are a high number of [unvaccinated children], you’re going to get polio cases.”

Without consistent efforts to try to finish the eradication job, polio will move, Zaffran said. “If we stop the effort, the virus is not going to ask for permission to cross the border.”

There’s recent evidence that underscores his warning. In May, the WHO reported that poliovirus was found in sewage in southern Iran, which has not recorded a case of polio since 1997 and hasn’t seen polioviruses in sewage — a standard way countries do surveillance for polio — since 2001.

Polioviruses shouldn’t be floating in sewage in a country that hasn’t had polio cases for more than 20 years. Analysis of the virus showed it came from Pakistan; someone who contracted it there traveled to this part of Iran. People infected with polio emit viruses in their stools during and for several weeks after infection.

If polioviruses were to break out of Afghanistan and Pakistan, there is no guarantee the United States — with its clusters of unvaccinated children — wouldn’t again see paralytic polio, Orenstein said. “As long as there are pockets of [susceptible children] we run the risk.”

Orenstein said when he talks to funders about polio he makes the case that this isn’t just a humanitarian effort — that there are domestic health security concerns for donor countries too.

This far into an eradication effort is a risky time, Moss suggested.

“I think the lesson is that … when you make progress in reducing the incidence or transmission of a pathogen like measles virus or poliovirus, and particularly as you move toward eradication, if there are lapses — whether that’s due to fatigue or from resistance in communities — there’s an extremely high risk,” he said. “It’s almost inevitable that you’re going to have outbreaks and move backwards.”