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During 2017, hundreds of thousands of people spent their working hours, and weeks and months of volunteer time, on an elusive goal: trying to snuff a handful of stubborn diseases out of existence.
Some of those diseases—like polio, Guinea worm, and river blindness—currently cause only a handful of cases. That public health workers have been chasing them for decades, spending billions of dollars in the process, elevates the effort to quixotic. But there’s a hidden motivation to their work. Every year they work to vanquish these infections, they’re training for a much bigger campaign to come: wiping out measles, one of the most infectious viruses on the planet.
Defeating measles has long been a cherished dream in global health. Just in 2016, according to the World Health Organization, the disease infected more than 20 million people and killed almost 90,000 children. But no one is even sure when such a campaign might begin. Opposing camps within public health argue either that the time is now, to piggyback on top of current campaigns, or after polio is gone, because we can only fund and focus on one global disease at a time. In other words: Is the best way to end measles in the future by not ending measles now? Could the failures—and near-successes—of other eradication campaigns ultimately teach us how to conquer measles?
After the thrill of eradicating smallpox, declared gone from the world in 1980 after a 14-year effort, global health planners dreamed big dreams about the other diseases they would vanquish. But in the years since, eradication efforts stalled. The campaign against Guinea worm has been going since 1980; polio, since 1988; river blindness, in the Americas, since 1992.
Smallpox had been chosen not just because it was a killer, but because it possessed qualities that made eradication plausible. It affected only humans and couldn’t hide in animals or the environment. It produced visible signs of illness, quickly—epidemiologists could easily trace who had infected whom—and its symptoms were unique. And it could be prevented with just one dose of a vaccine.
As it happens, measles fits those conditions too—more so than the other diseases that have been in public health’s sights since. It has no nonhuman host. It can be detected with a reliable diagnostic test. And it can be prevented with a single vaccine dose (though kids in the United States get two childhood doses, just to be sure).
But the smallpox vaccine was delivered in a uniquely low-tech way, jabbed into the skin with a forked needle that held a drop of vaccine between its tines. The measles vaccine uses a syringe, which requires trained healthcare personnel and safe sharps disposal. And measles in the 1980s (and even now) was everywhere, a routine disease in most of the world.
So, instead, global planners chose polio, which then caused about 350,000 cases of paralysis per year. It could be prevented by a simple oral vaccine, and polio had already been eliminated from North and South America, which made global success seem plausible.
But polio was more complicated than anyone knew. Faults in vaccine transportation, and sometimes quirks in the biology of the gut, where the virus replicates, meant that it could take many more doses than anticipated to create immunity. Then researchers discovered the vaccine’s weakened virus could mutate to regain its strength, causing outbreaks identical to the wild virus.
The campaign’s 2000 deadline came and went. Other hopeful end dates did too. By last year, there were only 21 cases of wild polio in the world—but there also were 86 cases of vaccine-derived polio.
The cases caused by wild virus are in Afghanistan and Pakistan, places that everyone always understood would be difficult. But the cases caused by the vaccine move around the map, made possible by wars and unrest that prevent vaccinators getting to children. In 2017, those were Syria and the Democratic Republic of the Congo, and in 2016, the parts of the Lake Chad basin overlapping northern Nigeria that are controlled by the terrorist group Boko Haram.
A dark gift of eradication campaigns is that their intense focus on a disease reveals things that research had never recognized before. It wasn’t until the polio campaign began that vaccine-derived polio was even discovered. Years down the line, scientists have realized the mutated virus can be a long-lasting risk. It can reproduce for years in the guts of people with certain immune system disorders, making them permanent emitters of infectious virus that passes into sewage. That’s driven development of new antiviral drugs to give to those long-term excreters, to prevent them from being the disease’s last refuge.
“It is always the last mile that is so difficult,” says Mark McKinley, who leads a project at the Atlanta-based Task Force for Global Health to develop two polio antivirals. “You learn things you didn’t know and uncover aspects of the problem you didn’t appreciate.”
That turned out to be true for Guinea worm as well, a parasitic disease that occurs when people unknowingly drink larvae floating in stagnant water. After a year of incubation, the larvae form a yard-long worm and break through the skin. There is no vaccine to prevent it and no drug that kills the larvae; the only treatment is to slowly pull the worm out, which can take months.
The essence of the campaign against it, which was created by the Carter Center in Atlanta and is now led by Donald Hopkins, a physician and epidemiologist who was in the thick of the smallpox campaign, is to keep infected people from accidentally fouling water sources, and to persuade villages at risk to filter their drinking water. And it has worked. In 2017, there were just 30 cases, down from 3 million in 1980.
But as with polio, Guinea worm had a surprise in store. As Hopkins told me, the parasite has found a new home in stray dogs, which may have picked it up from eating fish guts dumped by villagers. Infected dogs, wading in for a drink, recontaminate ponds and streams. As with smallpox and polio, the Guinea worm campaign presumed the disease it targeted had no nonhuman host. Instead, the infection has found a new niche to hide in.
The challenges don’t stop with the diseases’ biological ingenuity. River blindness, a parasitic disease transmitted by flies, has been eliminated in most of the Americas thanks to a donated drug. But it hangs on stubbornly in a pocket on the Brazil-Venezuela border, where illegal mining operations make it impossible to get treatment to the Yanomami tribe. “The challenges are transport, the cost of operating in these remote areas, and frankly political will,” says Frank Richards, a tropical-disease physician who leads the program on river blindness at the Carter Center. “Brazil and Venezuela both have problems that seem a lot bigger to them than river blindness.” In river blindness, in other words, there’s a government failure, and also a civic one.
Though the United States and Western Europe aren’t the Amazonian jungle, those same challenges lie in wait for any measles campaign to come. Even in areas where that disease has been fought to a standstill—endemic cases in the US were eliminated in 2016—it has recurred because the virus can find a foothold in vulnerable populations. In the US, where measles vaccination is mandatory for children, most of that vulnerability has been created by parents refusing the vaccine for their kids.
That was the main driver in 2014 of 383 measles cases in Amish communities in Ohio, and in 2015 of 147 cases in a multistate outbreak that began at Disneyland. However: Along with unvaccinated children, the Disneyland outbreak included six children who got the measles vaccine, but didn’t develop immunity. That suggests that any future measles campaign will face unpredicted surprises, just as the polio and Guinea worm campaigns did.
The cost of eradicating measles has been predicted to be $7 billion to $14 billion; the benefits are only realized later. Though they are huge: A study earlier this month by researchers from Harvard, Gavi, the Vaccine Alliance, and elsewhere predicted that fully vaccinating against measles would save more than 22 million lives by 2030, and keep almost 5 million people from falling into poverty.
Long-time campaigners are counting on a measles campaign to ignite a new fervor for public health work. Richards, who was in medical school during the smallpox campaign, remembers being inspired by stories of what it took to eradicate history’s worst killer. “Here we are at 99.99 percent,” he says. “In any other public health program, you would be getting high fives and raises and be on to the next thing.” Instead, they’re continuing on—to ensure the next campaign’s success.
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