A fool’s errand? Eliminating mosquitoes to end disease epidemics

Eighty years ago, one man set out to eradicate the deadly insect that now causes Zika—and it sullied his legacy forever.

It’s June 5, 1928, and Fred L. Soper is living in Rio de Janeiro when the Yellow Fever outbreak hits.

“Newspapers in North have reported 70 cases in Rio,” Soper writes in his diary in early June. And the next week: “Wild rumors are heard that Bahia is full of Yellow Fever and Santos has ever so many cases.”

According to science historian Nancy Leys Stepan, author of the book Eradication: Ridding the World of Diseases Forever? no one had seen this outbreak coming. “That was a total surprise,” says Stepan. “The Brazilians had a very good record actually of controlling Yellow Fever.

In Soper’s opinion, this outbreak could have—should have—been prevented. Brazil’s health department hadn’t been vigilant enough about monitoring yellow fever, he thinks. It was a failure of administration.

But if there’s one thing Fred Soper can do, it’s administrate.

“The Commander” takes charge

At this point in time, Soper had just spent seven years organizing health campaigns in Brazil and Paraguay, fighting hookworm disease with the Rockefeller Foundation. And he didn’t get the nickname “The Commander” for nothing.

“He had a very upright bearing, a moustache. He looked rather like a soldier,” says Stepan. “He conducted himself rather like a, not a just a soldier I would say, but a general.”

Soper, left, during his time at the Rockefeller Foundation’s International Division in Brazil. (Courtesy of Fred L. Soper)

Shortly after the outbreak, Brazil’s Yellow Fever service is reorganized under Soper’s command. And to him, the path forward is clear—with hard work and organization, he thinks that he can eradicate yellow fever for good. He just needs to figure out how.

The disease, health officials understand, is carried by the Aedes aegypti mosquito, and Brazil has brigades of inspectors who go around patrolling for the insects. For three months, Soper follows these inspectors all around the Northeast of Brazil—going from house to house, destroying their breeding places, and keeping meticulous records. And this, Soper comes to think, is how you eradicate a disease—by eliminating the insect spreading it. Soon he assigns brigades to do the same thing all across Brazil.

“He had this idea of the perfection of public health administration,” Stepan reflects. “That you could achieve your goals if you were completely perfect in everything that you did. And since the world is not perfect, things did go wrong.”

Things promptly go wrong for Soper.

For a long time, everyone had thought that yellow fever could only exist in mosquitoes or in humans. But a few years after the outbreak, scientists discover that monkeys living in the rainforests can also harbor a variant the disease, meaning that the only way to truly eradicate the disease would be to exterminate all the monkeys—which no one is eager to do.

The discovery of so-called “jungle” Yellow Fever puts a kink in Soper’s plan. Up until now, eradicating the disease has been his main goal. With that no longer possible, he starts to change his focus.

The most perfect solution

It was an idea had actually been stirring in Soper’s mind for years, first appearing in his diary the year before the outbreak:

Some thoughts that came to me this morning. Is It Possible To Exterminate Aedes Aegypti In Limited Control Areas? Has Extermination Ever Been Attempted? … This may seem a bit wild, but it does not seem to me to be any more of a departure from the reasonable than was the first attempt to control yellow fever by antilarval measures alone. It seems to me to be worth investigation.

Maybe he can’t eradicate yellow fever. But what if he eradicated the mosquito that causes it?

“It seems paradoxical in a way because you give up the eradication of a disease and you transfer your ideas of eradication to the insect,” says Stepan. “Insects are extremely difficult animals to think of eradicating.”

(That is, they’re small, and quite good at adapting. Mosquitoes have been around since the Jurassic period, and are found on every continent but Antarctica.)

Still, Soper’s idea isn’t completely off the wall. It’s based on the fact that, in a city like Rio de Janeiro, if you can get to the point where five percent of houses or less have these mosquitos, that will be enough to prevent Yellow Fever from spreading. But then that scientific fact gets distorted through Soper’s perfectionist lens.

Soper starts to realize, if you do a good enough job to kill 95 percent of mosquitoes, you’re likely going to end up killing 100 percent of mosquitoes. So why not just aim for complete success?

“And then he became converted to the idea,” says Stepan. “‘Well, we could eradicate this mosquito and if we did that we would no longer have yellow fever epidemics at all.'”

To be clear: There are other ways to control Yellow Fever, and Soper is choosing an ambitious, difficult path. There’s a world of difference between controlling a disease and eradicating a species from a country of three million square miles like Brazil.

Disease experts mock him. Insect experts remind him that those last five percent will be nearly impossible to find. Even the Rockefeller Foundation, who he works for, thinks that eradicating a mosquito isn’t what they came here to do. None of which matters to Fred Soper.

“He was very, very convinced that he had the answer,” says Stepan. As Soper himself would later recall this moment: “The aegypti mosquito was now the enemy rather than Yellow Fever. The eradication of aegypti would prevent not only yellow fever but also dengue and any other aegypti-transmitted disease.”

“The Mussolini of Brazil”

Soper’s plan soon receives government sanction. In October 1930, shortly after he takes over the Yellow Fever program, there’s a revolution in Brazil. Getulio Vargas overthrows the elected government in a coup. “He was an authoritarian, often called the Mussolini of Brazil,” adds Stepan.

Soper quickly calls a meeting with this new leader, and the pair hit it off. Vargas gives Soper permission to do whatever he needs to do—and now, Soper’s dream of eradication starts to look feasible.

All over the country, his mosquito brigades are authorized to fumigate people’s houses with insecticide. If they find mosquitoes breeding in a house, they get to impose fines on the owners. When someone in a suspect area dies of unknown causes, Soper sends a worker to the funeral, where they cut out a chunk of the deceased person’s liver, to be biopsied—with or without the family’s permission. At one point, a newspaper calls this new law “draconian,” and one of Soper’s colleagues suggests that the government should censor such criticism.

“But I pointed out that it was draconian and the fact should be well known before the Service started to enforce it,” Soper would later recall.

The strategy seems to work. By 1940, Aedes aegypti had disappeared from six Brazilian states and all of Rio de Janeiro.

By this point, even though a vaccine for yellow fever has been developed, Soper still insists that mosquito eradication is the best way to get rid of the disease in the long term. And in his defense, that seemingly impossible goal is looking more and more likely every year.

‘He who rides the tiger may not dismount—so long as the tiger lives!’

“The first serious proposal that I leave Brazil had come shortly after the attack on Pearl Harbor,” Soper would write in his memoirs.

When World War II begins, the US Army calls on Soper for his expertise. With his eradication campaign in Brazil firmly on the right track, Soper leaves. He spends the next four years fighting malaria in Egypt, preventing typhus in Italy, experimenting with the use of DDT—and saving millions of lives along the way.

But all along, Aedes aegypti remains in the back of his mind, this goal that’s just within reach.

After the war, Soper is appointed director of a new organization called the Pan-American Sanitary Bureau. And he sees his chance to make eradication happen not just in Brazil, but across the American continent. “And he sets this in motion and literally criss crosses the Americas trying to make governments commit themselves … to achieving this end,” says Stepan.

And he succeeds. Country after country sets up programs like the one he’d been running in Brazil. After ten years, in 1958, for the first time ever, the World Health Organization certifies entire countries as free of Aedes aegypti. Brazil, Bolivia, Belize, Ecuador, French Guiana, Nicaragua. Panama, Paraguay, Peru, and Uruguay are certified first. After this, even more countries sign on to the campaign.

Soper has become the godfather of eradication. He starts giving lectures to medical students and health workers. His notes are full of dramatic aphorisms like, “Administration is the essence of eradication,” and “He who rides the tiger may not dismount—so long as the tiger lives!”

Because even as the concept of eradication is spreading across the continent, Soper is terrified that it’s all going to come crumbling down. As he should be.

“When you get to a very low rate when the when the mosquito becomes almost invisible…is precisely when public health agencies tend to give up,” says Stepan. “And as a consequence, almost inevitably, the mosquito comes back.”

Doubling down

A letter from Soper’s archives, dated August 22, 1967:

Dear Paolo: … The most immediate reason for this note is the news of the reinfestation of Belém do Para with Aedes Aegypti. …It is especially important that Brazil move immediately to eliminate this reinfestation and a the same time use every means to get the support of other countries now free of aegypti to insist on the completion of eradication.

“[By 1967] Soper is very shocked to discover that a large area of northeastern Amazon is infected by the insect,” says Stepan. “By that time Brazil had lost its certification free of Aedes aegypti.”

“So it had got it and then it had lost it.”

What happened? Once these countries were certified aegypti-free, it was hard to convince their leaders to keep dedicating time and money on those programs. Plus, it’s hard to say today whether they were truly eradicated in the first place. In other words, Soper’s detractors had been proven right. And the public health community, which had recently made a hero out of Soper starts to turn against him.

The next year, the director of the CDC publishes a lecture questioning whether the eradication of Aedes aegypti, Soper’s holy grail, is still worth pursuing. He points out that it hasn’t worked, and that they have vaccines against yellow fever. Can public health officials really keep asking these small, poor countries in Central America to pour money into eradication if there are better, cheaper options?

Soper responds with a letter in turn.

“I cannot remain silent in the face of these surprising proposals,” he states. And he doubles down on his failed strategy, imploring others to stay the course. “The long-term continuation of this freedom [from Yellow Fever] must be based on the recognition of Aedes aegypti as the enemy to be feared.”

It’s a refrain he’ll continue repeating for another nine years, to increasingly deaf ears, as country after country disbands its eradication program.

In 1977, Fred Soper dies in Wichita, Kansas, not far from his birthplace. No longer a laughing stock, no longer a hero—but somewhere in between.

“There’s no doubt that Soper in some ways has some attractive qualities,” says Stepan. “But I also worry that people would find a hero in him, when it’s not what I intended.”

We’re all Sopers now

Today, amid news reports that remind us daily of the danger of Zika—also transmitted by Aedes aegypti—it’s awfully tempting to say that Fred Soper knew something we didn’t. Like, that the mosquito wasn’t done with us.

“Of course he was quite wrong in one very important regard,” Stepan points out: “You can’t eradicate—he could not eradicate an insect. So he has not been vindicated in his eradicationist goals.”

But there are good lessons to be taken from Soper, says Stepan.

“Is his determination, his conviction of the importance of getting the details right and so on—has that been confirmed? Yes, I think in that in many respects it has been. It takes a certain kind of person to do that work well, and he did it well.”

For us, as for Soper, eradication seems like such a sleek, perfect solution. Nowadays we have technology, like genetically engineered mosquitoes, that threatens to make Sopers out of all of us.

The question is, which Soper will we become? The Commander, whose diligent administrating saved countless lives? Or the authoritarian whose devotion to an idea blurred his good sense? In the age of Zika, we may find out soon enough.