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A year ago, the most pressing concern leading up to the Olympics this summer in Brazil was that swimmers and sailors would compete in Rio’s sewage-laden Guanabara Bay. Today, one fear looms above the rest as the country prepares to welcome the world for the games this summer: Zika.

A year since it emerged from northeast Brazil and grabbed international headlines, the mosquito-borne Zika virus is still “spreading explosively,” the . So far, an estimated one million people have been infected across Latin America, from Paraguay to Mexico. Unchecked, the WHO has warned, the disease could infect four million more before the year is out. Its symptoms include fevers, rashes, joint pain and, in pregnant women, the possibility of a child born with microcephaly—a birth defect that leads to abnormally small heads and underdeveloped brains. The disease is nowhere near as deadly or virulent as, say, Ebola, but it inspires a similar horror and the pregnant women to avoid travel to epidemic regions.

“The problem with Zika is that, for one particular target population, it is very bad,” says Scott Weaver, the scientific director of the Galveston National Lab at the University of Texas and one of the few researchers who studied Zika before the current outbreak. “Your perspective gets distorted when you see babies with microcephaly. It’s heartbreaking.” In Brazil, officials have reported .

Brazilian authorities are working around the clock, but it’s doubtful the epidemic will be contained by the start of the Games in August. “We do not have a vaccine for Zika yet,” Brazilian president Dilma Rousseff earlier this year. “The only thing we can do is fight the mosquito.”

That, unfortunately, is not a simple proposition.

The fight against disease-ridden mosquitos is a battle nearly as old as civilization. Ancient Egyptians consumed vast amounts of garlic to ward off mosquitos while they built the pyramids; Romans drained swamps to combat malaria outbreaks; the U.S. cleared mosquito-infested jungle to protect workers constructing the Panama Canal. And yet, as each outbreak of West Nile in New York or malaria shows, controlling mosquitoes is a fight we’re nowhere near winning.

The enemy in Brazil is Aedes aegypti. One millimeter long, black and white, and thirsty for human blood, Ae. aegypti is not only the main transmitter of Zika—it’s also the biggest vector of yellow fever, chikungunya, and dengue, a.k.a. bone break fever. Over its history, this particular species has been the ferrier of untold human suffering, filling city morgues from Philadelphia to Buenos Aires, changing the course of wars, and felling presidents and peasants.

Because of the mosquito’s prevalence across the Americas, from Philly to Patagonia, even cities thousands of miles from Rio are at risk of an outbreak this summer, experts say. “They’re like hurricanes,” says Gordon Patterson, a historian of mosquito control at the Florida Institute of Technology, referring to the outbreaks. “We don’t know where they’re going to hit, but there’s a storm out there on the horizon.”

This year, governments and charities across the world will spend hundreds of millions of dollars fighting mosquitos. And still, a million people will likely die from mosquito-borne diseases. To stop an illness like Zika, humanity has to best one of its oldest enemies. Is it even possible for Brazil—a single nation and only “newly industrialized,” according to economists—to kill or subdue a swarm of millions of tiny mosquitos and stop an epidemic?

Well, the country’s done it before.

When Dr. Fred Soper, a 27-year-old epidemiologist from Kansas, arrived in Brazil in 1920, the knowledge that mosquitos transmit disease was barely 30 years old. Before that seminal discovery, made by Ronald Ross in 1897, experts believed malaria and yellow fever preyed on the morally corrupt or were spread through “bad air.” Brazil, with its tropical climate and marshy landscape, represented the front line of humanity’s nascent efforts to fight insect-borne diseases by targeting the bugs themselves. Soper was in town to spread the gospel of “mosquito control.”

Though he had little tropical medical experience, Soper was sent to the country by the Rockefeller Foundation, which was then dedicated to ridding the world of malaria, yellow fever, and other diseases carried by mosquitos. Straight-backed, bespectacled, and sporting an immaculate mustache, Soper was a commanding figure in the field. Though he stood just five foot eight inches, he had “the presence of a giant” and “seemed equally capable of browbeating man or mosquito,” wrote the late Harvard entomologist Andrew Spielman in . Improbably, Soper’s actions in Brazil would change the field of public health forever.

It’s difficult to overstate the damage mosquitos inflicted on the human race during the early 20th century. In Soper’s day, yellow fever and malaria regularly killed several million people around the globe each year. They were viscous, virulent diseases that left whole regions ravaged. The men—and they were mostly men at the time—who dedicated their lives to fighting mosquitos were widely viewed as public health crusaders. William Gorgas, the American who drove yellow fever and malaria from Havana after the Spanish American War, was knighted in England for his work. Walter Reed, who discovered that mosquitos transmit yellow fever, is still a towering figure in American public health.

Though great strides had already been made against yellow fever—modern plumbing and simple window screens did much to staunch epidemics—periodic outbreaks persisted in Brazil in the 1920s, particularly in the country’s rural northeast. In May of 1928, after a 20-year absence, newspapers began feverishly reporting rumors of yellow fever in Rio de Janeiro. Panic began to seed in the capital. Soper, then 34, went to investigate.

On May 31, Soper visited a 19-year-old patient who had been taken to the hospital with symptoms consistent with yellow fever. The patient “was semi delirious, with ‘walled’ eyes and continuously mumbling and calling out ‘mama’, etc.,” Soper wrote in his diary that day. “Respiration very rapid and not too deep. Pillows and sheet soiled with some black clotted material and with stains of red blood.” The man died the next day and Soper attended the autopsy. The results were conclusive. “There is no doubt but that this case is yf,” or yellow fever, he wrote.

Until then, cariocas—citizens of of Rio, the country’s most important city—had thought their city rid forever of the disease. Alarmed and overwhelmed, the government awarded the Rockefeller Foundation full authority to handle the outbreak—“carte blanche as far as yf is concerned,” Soper wrote. The next year, Brazil created the Cooperative Yellow Fever Service and made Soper, a foreigner, co-director along with the country’s director of public health, Dr. Clementino Fraga.

Yellow fever, like Zika, is spread by Ae. aegypti. The insect is a native of Africa and evolved to live in close proximity with humans. It likely arrived in the New World on slave ships and lives in any small pool of standing water it can find—in old tires, potted plants, even upside-down bottle caps. It bites humans repeatedly during the daytime. Then, as now, the best way to stop the spread of disease was to go after the bug where it lived.

“The most effective thing to do is to get rid of their breeding habitat,” says Joe Conlon, a former Navy entomologist and spokesman for the in New Jersey. “That’s easier said than done.”

But Soper had the full cooperation of the Brazilian government: The imposing Midwesterner wielded the thousands of employees at his disposal with the authority of a commander enforcing martial law, Spielman writes. From 1929 to 1932, Soper and his team went door-to-door across the country, forcing Brazilians to drain any standing water on their property, spraying larvicide, and fumigating homes. Yellow fever servicemen inspected cisterns and climbed on roofs to check gutters. Citizens had little choice but to comply with the inspections. Recorded details of these home visits are limited, but it’s not hard to imagine how they might go awry. At least one mosquito man was killed, Soper wrote, after entering a “man’s room against the orders of a householder.”

Soper himself lost nearly 30 pounds in the effort. His daily diary chronicled his constant travels around the country by boat, tallying the dead and rarely resting:

January 6, 1929 — Miguel Jose Santa’Anna died of yellow fever in Bahia.

October 12, 1929 — Officially a holiday. Spend day at Laboratory.

August 10, 1930 — Sunday. ERR and I go to hospital where he demonstrates the delicate art of snagging out liver sections [which were used to confirm yellow fever in cadavers] without touching the body or the sections.

August 15, 1930 — Assumption Day and a full holiday for everybody except the yf service.

By 1934, Ae. aegypti had been eliminated in most of the country’s population centers. But sporadic outbreaks still occurred in the countryside. To stop the disease entirely, Soper believed, the Cooperative Yellow Fever Service needed to transition from the preventative approach of managing mosquito numbers to eradicating the creature and the diseases it carries entirely—an objective so audacious that it was nearly unthinkable at the time.

“Eradication is neither easy nor cheap; it is most difficult and expensive, requiring a type of coverage and careful administration not dreamed of in most public health programs,” Soper wrote in a paper on the efforts. “The eradicator knows that his success is not measured by what has been accomplished but, rather…the extent of his failure [is] indicated by what remains to be done. He must stamp out the last embers of infection in his jurisdiction. His slogan must be ‘Any is too many.’”

During Soper’s crusade, a different invasive African mosquito, called Anopheles gambiae, one of the most efficient malaria vectors on earth, was wreaking havoc on Brazil. By 1938, Brazil was experiencing the largest malaria epidemic in the history of the Americas. More than 150,000 people were infected and 20,000 died. The Rockefeller Foundation’s scientists were terrified. From Brazil, the mosquito could colonize the rest of the Western Hemisphere and move into America. Soper was assigned 4,000 new workers and full authority to stamp out the epidemic by any means necessary.

With the blessing of Brazil’s dictatorial leader, Getúlio Vargas, Soper deployed “anti-malaria brigades” empowered to enter any property, inspect any building, and use force against anyone who intervened. In less than two years, the campaign managed to extirpate Anopheles gambiae from nearly all of Brazil. “Soper and his four thousand brigadiers had, it seemed, saved the Americas from the world’s most dangerous malaria vector,” Spielman writes. The doctor was feted by international leaders and Brazil minted a coin in his honor. Spielman writes: “Soper’s victory came to be regarded as one of the greatest public health achievements in history.”

During this period, Soper learned about a new, remarkably effective pesticide called dichlorodiphenyltrichloroethane—DDT, for short. Upon his recommendation, the U.S. Army began treating the uniforms of soldiers across the European theater during World War II to fight typhus spread by lice. When the war ended, Soper was widely respected as the greatest pest-killer alive—a genuine public health hero. Armed with the miracle mist, the cooperation of WHO countries, and a staggering $1 billion grant from the U.S., Soper’s dream of worldwide mosquito eradication seemed within reach. 

In 1955, using techniques developed in Brazil and metric tons of DDT, the Global Malaria Eradication Campaign codified Soper’s approach and took it international. The program was, at first, a wild success. Dozens of countries across Europe, Oceana and the Caribbean became-malaria free. “They used that top down military approach—they went into your house whether you liked it or not and it worked very well,” the American Mosquito Control Association’s Conlon says.

But there was a problem. DDT, the mosquito men’s wonder weapon, came with complications. First, the mosquitos developed resistance to the insecticide within five years. And second, as famously detailed in the 1962 book Silent Spring, DDT does a lot more than just kill mosquitos. The chemical wreaks havoc on eagles and other large predators and may harm humans, too. In America, after a generation of children grew up chasing the DDT trucks down suburban streets, the insecticide became a boogeyman nearly overnight. 

Other countries in the Western Hemisphere overlooked DDT’s potential hazards and diligently continued their war on the mosquito. But America—funder of the campaign, home to the intellectual founders of the eradication movement—held back, to Soper’s chagrin. “The principal delinquent in this international effort,” Soper warned in 1963, “is the United States of America.”

Ultimately, Soper’s war on mosquitos failed. Though Ae. aegypti had been eradicated from Brazil and much of Latin America, malaria still tormented most of the world. His hard-won victories were reevaluated by a new generation of scholars and entomologists, as well. Detractors pointed out that, rather than work with local Brazilians and improve living conditions among the rural poor, Soper focused his efforts and his millions of dollars of funds exclusively on his extermination project. His critics called his work in Brazil medical colonialism. 

“Soper ignored the social and economic conditions within which the malaria occurred,” wrote Randall M. Packard, then of Emory University, in 1994. “By doing so he lay the foundation for both the successes and failures of the great postwar malaria eradication programs.”

After a lifetime circling the globe in the name of public health, Soper died in his home state of Kansas, in Wichita, in 1979. Within a few years of his death, the Ae. aegypti that had escaped elimination in America had marched south, back across the New World, and were once again causing outbreaks in Brazil.

Today, Brazil is again lousy with Ae. aegypti, and the ferocity of the Zika epidemic is proof of the mosquito’s dominion over the country. Earlier this month, the Centers for Disease Control and Prevention called Zika “scarier than we originally thought,” and warned that the virus is linked to a broader set of concerns for pregnant mothers, including premature birth and eye problems in babies.  

Brazilian officials are working with health organizations around the world and taking an “all of the above” approach to containing Ae. aegypti that includes the newest, most exciting technological approaches. Everything is being pursued, from genetically modifying mosquitos with “kill switches” that cause premature deaths in offspring, to irradiating the bugs to make them sterile. 

But those are likely won't halt Zika's onslaught for one simple reason: they fall short of the type of take-no-prisoners, door-to-door campaign of eradication Soper waged 80 years ago. That kind of single-minded approach seems all but impossible today.

“[Soper] used to say that, if you have a democracy, you can’t have eradication,” a colleague of Soper’s in 2001. “When Soper was looking for a job at Johns Hopkins—this would have been 1946—he told a friend that, ‘They turned me down because they said I was a fascist.’”

Casting aside moral qualms with Soper’s methods, experts concede that his shoe-leather approach would be the most effective means of fighting Zika and other mosquito-borne diseases today. “I take my lessons from what was successfully done in the ‘50s in Latin America,” says Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and a fixture at congressional hearings on mosquito-borne diseases. 

In the U.S., Hotez says, we’ve heeded almost none of the lessons we learned from Soper’s coordinated, centralized approach. “There are over 700 mosquito control divisions all over the U.S.—some good, some not so good,” he says. “There’s no harmonization of practices. Everyone’s doing different things. And there’s no coordination.”

What you’ll see in poorer areas of the American South, for example, Hotez says, are dilapidated houses with no window screens and standing water in discarded tires and garbage piles. “This creates the perfect storm for the Aedes aegypti mosquito,” he says. “There is no such thing as a ‘small’ Zika outbreak in the Gulf Coast. If there’s a cluster of microcephaly cases in poor neighborhoods in Louisiana and or Texas, it would be compared to Katrina or the BP oil spill, and should be treated as such.”

When experts talk of dealing with Ae. aegypti now, few call for eradication. The prudent, more achievable course—reducing the bug’s population enough to stop the transmission of the disease—is all anyone can hope for.

Dan Strickman, an entomologist with the Bill and Melinda Gates Foundation, spends his days thinking about the best way to fight mosquito-borne diseases. “Fred Soper was an amazing person,” he says. But when asked about the prospect of eradicating Ae. aegypti again, Strickman demurs.

“There’d be an awful lot of benefit [from the kind of campaign] the Rockefeller Foundation promoted in the ‘30s—one that was systematic and sober and not based so much on enthusiasm about new science,” he says.

“My hesitation is: you hate to promote something that you doubt can be actually be done,” Strickman says. “Well, technically it can be done. We know that. But accomplishing it in today’s world? That takes some discussion. We’re not in 1930 anymore.”