Portside

Puerto Rico's Martin Peña canal is a winding, heavily polluted waterway that snakes 3.7 miles through the center of San Juan. Eight small, deeply impoverished communities, all lacking an efficient sewage system, surround the channel, and have for generations dumped untreated waste directly into the mud-colored water. One Friday in late April, it rained torrentially all night, turning the narrow streets into waist-high, foul-smelling rivers, washing away furniture, appliances, clothing and cars. Some degree of flooding happens about 20 times a year, and signs are posted along the canal advising, in Spanish, that "contact with the water may cause illness." In the past, the health risks have included gastrointestinal ailments, as well as mosquito-borne viruses, like dengue fever. This spring, another mosquito-related illness, the Zika virus, was added to the list.

On the Sunday after this deluge, I visit the tiny community of Buena Vista Hato Rey, which is drying out after a day of 90-degree heat. Navigating around gigantic mud puddles, I find my way to the small, one-story home of Dolores Perez, who is standing in her courtyard surrounded by her soggy possessions: rugs, jeans, sweatshirts, a hair dryer. She's lived in the house for 43 years, she tells me, and had lain awake all of Friday night waiting for the flood, which she and her family eventually managed to push back with brooms, mops and dustpans. This time, they'd been able to save their furniture, she said; in the future, who could tell?

The Perez family, thanks to their damaged pipes, hadn't had running water in about a year. "We called the water company 11 times – finally they tell us, 'Get a plumber,'" Perez's brother says, wryly. Yet there is plenty of standing water – in the streets, the gutters, the abandoned houses and empty lots – none of which the city of San Juan is able to do much about. If the water isn't removed, it is a near certainty that swarms of mosquitoes will be born in those pools, and at least some of them will carry Zika, which could, if public-health estimates are right, infect up to 875,000 of the island's 3.5 million people by the end of the year.

The specter of this plague, whose true impact may take months to emerge, looms over Puerto Rico, the largely impoverished island territory, roughly the size of Connecticut, that has become the Zika epicenter for the United States. Of the 1,301 mosquito-borne cases recorded in the U.S., 97 percent of them are in Puerto Rico, neither a state nor a sovereign nation, but whose people are, nonetheless, U.S. citizens. As of early June, the start of Puerto Rico's long, hot and rainy summer, there are 1,259 recorded cases on the island, though some health officials believe the true number may be more than 80,000.

In February, the Obama administration requested $1.9 billion in emergency aid to combat Zika, but Congress has yet to approve any funds. In May, the Senate put forth a bill to provide $1.1 billion, but House Republicans rejected the measure, instead proposing the government provide $622 million, most of which would be redirected from money set aside to fight Ebola and other infectious diseases. A week later, Congress broke for a 10-day recess without coming to a decision. Dr. Tom Frieden, head of the Centers for Disease Control and Prevention, told the National Press Club that he was shocked by the delay: "We have a narrow window of opportunity to scale up effective Zika-prevention measures, and that window of opportunity is closing."

Panicking that his state could soon face "disaster" as mosquito season approached, Florida Gov. Rick Scott, a Republican, wrote a letter to President Obama, beseeching him to make federal funds available. "Congress has failed to act, and now they are on vacation," he said.

In 2014, Congress agreed to spend $5.4 billion on the Ebola epidemic, and Frieden, who notes the CDC is still trying to stamp out Ebola in West Africa, said he "hopes that Congress will do the right thing with Zika." But unlike Ebola, which causes gruesome symptoms often followed by death, Zika is somewhat of a stealth virus. Most people infected will have no symptoms. Some may come down with conjunctivitis or break out in a skin rash, or experience muscle or joint pain or run a fever. Within a week or so, all of the symptoms, if they even emerged, are gone. In a certain number of cases, however, this may only be the beginning. Women who are infected with Zika during pregnancy run the risk of passing the virus to the fetus, which may then develop birth defects, the worst being microcephaly, a condition that causes babies to be born with undersize brains and heads. Depending on the severity, children with microcephaly may be stillborn or die shortly after birth, and those who live longer may require extensive, and expensive, medical care – the CDC estimates that it could cost $10 million to care for one microcephalic child. Zika, which seems to be particularly drawn to neurological tissue, may also cause swelling of the brain or spinal cord in adults, and has been linked to Guillain-Barré syndrome, an autoimmune neurological condition that can cause severe, if usually temporary, paralysis.

But the scariest aspect of Zika is how little scientists actually know about it. "There's a surprise a day with this virus," says Dr. Lyle Petersen, director of the CDC's division of vector-borne diseases, which are illnesses spread by arthropods like mosquitoes and ticks. Zika is spread by the Aëdes aegypti, the same mosquito that carries dengue, yellow fever and chikungunya. But Zika, notes Petersen, is the first virus since the rubella outbreak of the 1960s to cause major birth defects. Microcephaly may be just one of many complications. Researchers are also preparing for the possibility that Zika will cause a host of developmental problems that are, so far, unknown, and may take months or years to emerge. "That's really the untold story of this: We don't know the whole spectrum," says Petersen. "Are children that are born that look 'normal' really normal? That's going to take time, and some very sophisticated testing, to figure out."

Epidemiologists were surprised that a virus spread by mosquito could cause birth defects (rubella, they note, was spread by humans). Even more of a shock was that Zika could be sexually transmitted through semen. This is uncommon in vector-borne diseases, and it's a concern, says Petersen, because while mosquitoes are still the primary method of transmission, Zika lives in the blood for no more than a week or so. But the virus appears to linger much longer in other bodily fluids. "Does it mean that somebody can transmit [Zika] sexually four months after they've been infected? We don't really know that," he says. "And that's the problem. There is a lot we just don't know."

Zika was first discovered in 1947 in the Zika Forest of Uganda, where researchers were studying the impact of mosquito-borne viruses on rhesus monkeys. Over the next 60 years, there were only 14 documented cases of Zika in humans, mainly in Africa and parts of southern Asia. Then, in 2007, a Zika outbreak began on the tiny South Pacific island of Yap, where some 900 people were infected, though most had few or no symptoms. The next Zika outbreak occurred six years later, in 2013, when 31,000 people sought treatment for the virus in French Polynesia and its nearby islands. By 2014, Zika had spread to Brazil, where maternity wards in the summer of 2015 began to notice a strange new phenomenon: at first one or two, and then dozens of babies, born with small, almost pointed heads.

Although Brazil remains the hardest-hit, with perhaps 1.5 million Brazilians infected and more than 1,500 babies born with Zika-related microcephaly, Zika has since circled the globe, spreading across Latin America and the Caribbean, where there is active transmission of the virus in 41 countries and territories. Writing in the New England Journal of Medicine last winter, Dr. Anthony Fauci, director of the National Institute for Allergies and Infectious Disease at the National Institutes of Health, noted that Zika was just the latest mosquito-borne virus to reach the Western Hemisphere in the past 20 years, following the path of dengue fever, West Nile virus and chikungunya. This, he suggested, "forces us to confront a potential new disease-emergence phenomenon: pandemic expansion of multiple, heretofore relatively unimportant [mosquito-borne viruses] previously restricted to remote ecologic niches."

Three central factors contribute to the spread of these diseases, the first being climate change. Mosquitoes thrive in warm weather, and as temperatures rise, notes Petersen, "mosquitoes become more infectious, and they become more infectious faster." Outbreaks of West Nile virus, for instance, have happened during heat waves. Increased urbanization is also a major contributor, as is the recent explosion of global travel. Diseases like Zika "hitchhike in the blood," says the CDC's Frieden. "This is the new normal. We are a globalized and urbanized world, and diseases are just a plane ride away."

There are currently 618 confirmed cases of Zika in the continental U.S., among them 195 pregnant women, one of whom recently gave birth to a baby with microcephaly in New Jersey. She, like all of the people diagnosed with Zika, contracted the illness while traveling or living outside of the 50 states. There have also been some reports of sexual transmission in the U.S. and in Europe, including one case in France where Zika appears to have been transferred through oral sex. Though alarming, every case of sexual transmission has, so far, come from contact with people who were infected with the virus by a mosquito, says Petersen, who doesn't expect this to change. Zika might live in other bodily fluids longer than in blood, "but it's not six months," he says. "This is not going to be something like syphilis or gonorrhea."

Right now, scientists predict that while there may be an uptick in "imported" cases of Zika, the chances of a major Zika outbreak happening in the continental U.S. are fairly low – though Aëdes aegypti and its cousin Aëdes albopictus, which can also carry Zika, are endemic along the coasts and in the Southern U.S., leaving cities like Houston and Miami, and the Florida Keys, more vulnerable. Over the past decade, there have been small outbreaks of dengue and chikungunya in pockets of the U.S., including most recently a dengue outbreak in Hawaii, but these have been limited in scope, suggesting that Zika will likely follow the same pattern. That said, notes Petersen, "Obviously, this virus is not dengue or chikungunya, so I think we have to be prepared for transmission to occur in any place where the vector is present. Who knows what will happen?"

Even in the worst-case scenario, Petersen says, if the virus were to infect an entire city or region, there could be aerial spraying of mosquito-killing insecticide and warnings to pregnant women that they should avoid these infested areas. And given the prevalence of a host of factors, ranging from effective sanitation to the ubiquity of window screens and air conditioning, this kind of outbreak anywhere in the continental U.S., and much of Europe, for that matter, is unlikely. "I can't imagine a scenario where [Zika would be so widespread that] we'd say, 'Don't go to Florida,'" says Petersen. "I can see saying 'Don't go to Puerto Rico or parts of Miami.' But if what is happening in Puerto Rico was happening in Florida, it would be a national catastrophe."

Of the $1.9 billion the White House has requested for Zika, $828 million would go to the CDC to fund expanded mosquito-control programs, surveillance and public-education campaigns, both in the U.S. and internationally. Another $200 million would help fund the National Institutes of Health, the Food and Drug Administration and the Department of Health and Human Services to accelerate and possibly expand diagnostic testing and speed the creation of a vaccine, which scientists say won't be ready before 2018. The government has nixed any idea of performing mandatory, or even voluntary, testing on people returning from Zika-infested regions. "There are about 40 million travelers each year between the U.S. and areas with active Zika outbreaks," says Frieden. "You can't test everyone." Instead, the CDC's main priority is protecting pregnant women, the population most at risk. "That includes having them avoid travel to areas where Zika is spreading, and for travelers to use repellent upon return to prevent Zika from entering the U.S. mosquito population," he says.

About $750 million of the money Obama has requested for Zika would go to Puerto Rico, which in addition to undergoing a public-health disaster is also facing a $70 billion debt crisis. This has thrown the island's health care industry, the spending for which accounts for 20 percent of its gross domestic product, into particular crisis. Over the past year, Puerto Rico has been forced to cut back on a variety of health-related services, shuttering hospital wards, or even entire facilities, and delaying payments to the major insurers. The Puerto Rico Healthcare Crisis Coalition, a newly formed advocacy group, estimates that 3,000 doctors have left Puerto Rico since 2010, a steady brain drain that amounted last year to a loss of roughly one doctor per day. According to Dr. Victor Ramos, the head of Puerto Rico's College of Physicians and Surgeons, without immediate relief, the country's heath care system could collapse entirely by late summer.

Mosquito-borne illnesses, though not exclusively diseases of poverty, have a disproportionate impact on the poor, but urbanization, one of the key factors in the spread of all infectious disease, means that rich and poor invariably collide. One irony of San Juan is that some of its poorest and most trash-ridden neighborhoods are located just blocks from its financial center, known as the Golden Mile – indeed, the San Juan headquarters of the Swiss banking giant UBS, a major player in Puerto Rico's current debt crisis, looms over the slums, with which it shares the same sewer system.

This potent reminder of Puerto Rico's class divisions – not to mention the essential interconnectedness of those on both sides of this divide – is also a larger metaphor for the island's quasi-colonial relationship with the United States, which not only controls Puerto Rico's economic development, but also determines what it will be given by the federal government to address its most pressing local issues, including public health. Even after 1952, when Puerto Rico received its own constitution, its chief governing authority was still Congress, which has subjected the former colony to an inequitable system by which Puerto Ricans, who do not have a vote in Congress and cannot vote in federal elections, don't pay federal income tax, but do pay the same Medicare and Social Security taxes as those on the mainland – and receive roughly half of the entitlements as the states. Almost 50 percent of Puerto Rico's population lives below the poverty line, and close to 70 percent relies on some form of government-funded health care. The federal government covers $1.2 billion of the island's $2.5 billion in Medicaid costs, though that number will drop to less than $400 million once a temporary fund established by the Affordable Care Act in 2011 runs dry, which officials say could happen as soon as September 2017. In contrast, Mississippi, the poorest U.S. state – though not as poor as Puerto Rico – received $3.6 billion in 2014, more than 70 percent of its total bill.

What this has meant, explains Dr. Johnny Rullán, an epidemiologist who is also the island's former secretary of health, is that the federal government has given Puerto Ricans a choice: either ignore their poor or dig into their own pockets to provide them with health care. "Since we care about our poor people," says Rullán, "we chose [the latter], which puts us 1 to 2 billion dollars in debt a year," leaving the island no money for public health.

This inconvenient truth is just one of many intractable problems plaguing Puerto Rico, some of which pertain to the island's tangled finances, others to its messy relationship with Washington. But either way, Zika could easily push Puerto Rico over the edge. "They are completely, 100 percent overwhelmed, and they are facing a real health emergency," says Nicholas Prouty, a San Juan-based real estate investor and Democratic fundraiser who, since the Zika crisis began, has lobbied the White House to provide relief to Puerto Rico and other affected regions using the Stafford Disaster Relief and Emergency Assistance Act, which would allow the president to circumvent Congress.

"If we continue on the same path, the consequences of Zika for Puerto Rico will be devastating," Prouty says. He conjures a grim scenario of swarms of newly hatched mosquitoes, having incubated in the summer heat, emerging during a heavy rain from the countless discarded tires that currently litter the island. "This is when the situation metastasizes and reaches the tipping point," he says. "Add to it reduced garbage collection due to government austerity, and you got yourself the recipe for heartbreak" – babies born with deformities, and a massive infusion of public money needed to support them, for life.

Consider the short but pointed life of Aëdes aegypti, sometimes called the "cockroach mosquito." It is a carrier, or vector, of a host of diseases, from yellow fever to dengue to Zika, all of which have direct impact on humans. That is because, unlike some other mosquitoes – and there are 3,500 different species of mosquito, divided into 41 genus types – aegypti are human-centric. "These are mosquitoes that have quite literally co-evolved side by side with humans," says Dr. Tyler Sharp, the CDC's chief epidemiologist in Puerto Rico. "Most everybody on the island, myself included, have these mosquitoes in their homes, and that is because we are their main food source, and we provide them with their main habitat for reproduction, which is usually discarded trash."

Aegypti lay their eggs on anything that can accumulate water – old tires being a favorite, as well as Styrofoam containers, birdbaths, dog bowls, gutters and bottle caps. Once deposited, the eggs, which look like black smudges, can live up to a year. But once submerged in water, as during a heavy rain, they hatch, at which point they move quickly from larvae to pupae to, within about a week, full-grown mosquitoes, whose first objective, as Sharp puts it, is to find a "blood meal." Uniquely, while most mosquitoes live outdoors, aegypti prefer to live as close to us as possible: They can find homes under the bed, at the back of a closet, in the garage.

Only female aegypti carry Zika, which they acquire by biting a person with an active Zika infection. After that, the virus incubates inside the mosquito for about a week until it is ready to be transmitted to the next person she bites, who will then transmit the virus to the next mosquito. As aegypti rarely fly beyond a few hundred feet of where they were hatched (unlike other mosquitoes, which can travel miles), the entire human-to-mosquito-to-human transmission process happens in very limited space. "The more people there are, the more garbage there is, the more mosquitoes there are," says Sharp. "And the more mosquitoes there are, the greater the frequency of transmission of the pathogens."

The sheer destructiveness of aegypti has prompted scientists in both the public and private sectors to try to devise new ways to trap and kill mosquitoes, though there's still the question of how to reduce the risk of infection, period. "We're asking that question now," says Sharp, who works out of the CDC's Dengue Branch, which is located in a secure and secluded compound in eastern San Juan. Long before anyone heard of Zika, there was dengue, which has been endemic to Puerto Rico since the 1960s.

A new trap has been shown to reduce the risk of human infection by 50 percent, but it is costly. Is there actually an affordable intervention that works in terms of reducing human risk of infection?

"Um, not yet," Sharp admits.

In other words, right now, the mosquitoes are winning.

Early this past April, Claudia Moreno, a 27-year-old web producer, woke up one morning with what felt like a nasty hangover. She was exhausted and her head pounded. By afternoon, she'd also developed a fever and chills. Over the next few days, more symptoms emerged: severe joint and muscle pain at first, then an itchy and painful case of conjunctivitis, and most disturbingly, a bright reddish-orange rash that started on her face and spread over her entire body. "That's when I started to worry," she tells me when we meet in San Juan a few weeks later.

Claudia, who asked me to not use her real name, lives in a small and tidy apartment in Santurce, a gentrifying area sometimes called the "Brooklyn of San Juan." She is part of a younger generation who left Puerto Rico for college or grad school – in Claudia's case, a master's degree in Europe – but then returned to the island, where mosquitoes are simply a part of everyday life. In Claudia's apartment, which lacks both air conditioning and window screens, mosquitoes live in her bedroom closet, and they breed, she assumes, in bits of standing water in her potted herbs and hanging plants. During the first few days of her illness, Claudia assumed she had dengue fever. But when her boyfriend told her that he too was sick, she began to think it might be something else. After reading about Zika on the CDC's website, Claudia concluded that they probably had the virus, though whether through sex or mosquito, she wasn't sure. But either way, she didn't do much about it.

"I guess I could have gone to the doctor," she tells me as we sit drinking coffee on her terrace. But she didn't want to. Seeing a doctor on the island can take up an entire day. As many Puerto Ricans tell me, the wait to be seen can be so long at hospitals and local clinics, as well as in the offices of many private physicians, that people arrive as early as six in the morning to get their name on a list. "Then you have a four-hour period of people waiting [until] the doctor comes to the office, around 11:00," says Claudia. "Then he starts seeing patients at around 1:00. And so, if you don't get bored or if you don't, like, die, he's going to see you, at 6:00." She smiles. "If I'm not coughing blood, I'm not going to the doctor."

This, if indeed she had Zika (Claudia notes that since she was never diagnosed, she can't be certain), would make Claudia part of what health officials suspect is a hidden majority of Puerto Ricans who have had, or will get, the virus but will never receive a conclusive diagnosis, either because going to a doctor seemed like too much of a hassle, or they had no symptoms. Or even if they did, "some people don't want to know," says Dr. Brenda Rivera, chief epidemiologist for the Puerto Rico Department of Health.

A veterinarian by training, Rivera is managing a crisis-response team of local health workers, combined with specialists from CDC headquarters in Atlanta, all of whom work out of Puerto Rico's emergency-operations center, a large, sealed room where a gigantic screen projects an image of the Aëdes aegypti, with its signature white-striped legs, over a map of the island, shaded to reflect where Zika infections have been found. A huge digital clock above the map notes, on the day I visit, that it is the 21st minute of the third hour of the 76th day of the "Level 1" emergency response, the highest level assigned by the CDC.

Trying to get a handle on what the response consists of, though, is difficult, since right now the "crisis" is less a visceral, visible reality than it is a ticking time bomb. Of those individuals who do get their blood tested for Zika, it can take a month to get the results, which is true on the mainland as well. This, combined with the sheer ubiquity of mosquitoes, has led some people to shrug off testing. Aëdes aegypti are nervous creatures, "easily disturbed," as scientists put it, and go from one person to the next, biting perhaps four or five people in a single blood meal. It takes only one person with Zika to infect the mosquito, which, during its next meal, might infect a neighbor who is pregnant or wanting to be pregnant, or whose partner is pregnant. Each year, there are 30,000 babies born in Puerto Rico. If health officials' calculus is correct, about a quarter of them will be born to mothers who were at one point infected with Zika. How many will have microcephaly is still unknown. CDC researchers have postulated it could be anywhere from one percent to as high as 13 percent.

I never knew about microcephaly until now," says Dr. Carmen Zorilla, an obstetrician specializing in high-risk pregnancies at the University of Puerto Rico's medical center in San Juan, known as Centro Medico. In her office off the hospital's pediatrics unit, Zorilla, an elegant woman in her early sixties, is struggling to explain the strange and disturbing course of this most extreme of Zika's manifestations – which is not, she notes, the same as anencephaly, which is when a fetus simply doesn't have a brain. "These are fetuses that do have brains, but [they're] really small," she says. "You can see this on ultrasounds: The fetus has this normal-size head, and it has a scalp. And then all of a sudden the brain [looks like it] shrinks..." To illustrate, Zorilla cups one manicured hand over the other and then slowly slides it forward, as if pressing down on a ball, while searching for the appropriate English word for what happens next. "The brain looks like a prune," she says finally.

Even as scientists continue to learn more about Zika's impact on fetal development, what is currently known is that many women who get infected during their first trimester will have perfectly normal pregnancies, or at least what seems to be normal. And then each subsequent month presents new and more terrifying possibilities. "The problem is, even if the fetus is affected, you might not have ultrasound evidence of neurological damage until much later," says Zorilla. "If at all."

Adding to the unease is the international news coverage of Zika, much of it citing alarming proclamations from health officials – "Zika virus: 'Scarier than initially thought,'" CNN announced in April. Almost everyone I meet in San Juan brings up the immense publicity Zika has received in Puerto Rico, much of it by the mainland press, which has hurt tourism, the island's one genuinely thriving industry. The day I met Rivera, in fact, she was in the midst of trying to convince officials from Major League Baseball that, provided they use strong mosquito repellent, it was perfectly safe for the Miami Marlins and the Pittsburgh Pirates to come to San Juan to play a two-game series over Memorial Day weekend. But the league, citing some players' concerns over "contracting and potentially transmitting the Zika virus to their partners," canceled the games, moving the series to... Miami, where there are currently 50 Zika cases. Miami-Dade County, in fact, has been under an official state of emergency over Zika since February.

"The same chances you have to get Zika in Puerto Rico, you will have in Miami," Puerto Rico's governor, Alejandro Garcia Padilla, noted on C-SPAN. "It's offensive. It's just ignorant."

Shortly after leaving San Juan, I visit Lyle Petersen, who is heading up the CDC's Zika response from its main campus in Atlanta. A lanky Californian in his mid-fifties, Petersen was sent to Atlanta from the division of vector-borne diseases headquarters in Fort Collins, Colorado. There, and in Atlanta, he says, scientists are focusing on Zika, as well as yellow fever, which recently killed several hundred people in Angola. "And Lyme disease is totally out of control," he says.

Petersen's main specialty, however, is West Nile, a virus that was unknown in the Western Hemisphere until 1999, and then spread rapidly across the U.S. About 10 years ago, Petersen himself came down with West Nile virus after getting bitten by a mosquito somewhere between his front door and his mailbox. He spent most of the next few months in bed. "West Nile is in every state and causes thousands of people to die or become brain-damaged or paralyzed every year," he says. "And those aren't the tropical Aëdes mosquitoes – those are Culex mosquitoes, the type you find flying around everywhere."

Petersen speaks of West Nile to illustrate both the vast array of insect-borne viruses now lurking in our modern world and their tremendous cost. Months of political wrangling between Democrats and Republicans over Zika funds have focused on the details of Obama's $1.9 billion proposal, an open-ended plan that some GOP lawmakers have described as a "slush fund." Both the CDC's Frieden and Fauci from the NIH insist this is not just a blank check, but money necessary to combat Zika without "robbing Peter to pay Paul," as Frieden says. Fauci adds, "We asked for $1.9 billion because we need $1.9 billion."

Petersen, though, acknowledges that years of budget cuts at both the NIH and CDC have severely impacted the agencies' emergency preparedness. "Certainly we need money immediately to deal with this – it's a massive response," he says, as we sit in a glass-enclosed conference room overlooking the CDC's emergency-operations center, which seems to be empty. "There are hundreds of people working on Zika," he assures me. "But part of the problem is we haven't been able to build capacity over the past 15 years." America's public-health infrastructure tends to deal reactively with crises – hundreds of millions of dollars, for example, were spent to combat West Nile in the early 2000s. But once the initial crisis passed, says Petersen, "the whole system for monitoring and dealing with these diseases eroded. So now we have another crisis, and there is a critical lack of staffing to deal with these specific types of diseases."

And yet, ironically, he says, the rate of vector-borne diseases is only going up. This is due to social and environmental factors as well as lack of political will. Well before the West Nile virus gained a foothold in the Northeast, New York City had drastically cut back on its mosquito-control program. When the virus arrived, in 1999, the city was stuck with a skeleton crew. "When there is an absence of disease, politicians start to ask, 'Why are we funding these preventive public-health measures,'" says Dr. Laura Kahn, a research scholar with Princeton's Science and Global Security program. Kahn is a leader in the "one health" movement, an emerging public-health specialty linking human, animal and environmental health. "It's easy in the urban environment to feel separate from the natural world, but we are a part of the natural world, and it's not that diseases go away, it's that we've got them under control," she says. "As soon as we cut back on prevention, they start roaring back. But they can all be prevented," she adds, "if we had political leaders who made sure their people all had good sanitation, clean water and adequate sewage systems, to prevent mosquitoes from being able to proliferate."

Right now, there is no money. So far in 2016, Zika has cost the Puerto Rican economy more than $30 million in lost tourist revenue from canceled hotel reservations – a disaster for the island, now possibly weeks away from defaulting on an $800 million debt payment. During the time I spend on the island, in April, the Sunday edition of El Nuevo Dia, the island's main newspaper, reports that Puerto Rico's health care crisis has gotten so bad, one of the five managed-care companies contracted to provide low-income health care threatened to pull out of the program unless it was paid its share of the $21 million the government owed its health providers. Similar ultimatums have come from private companies providing services ranging from food for prisons to, most recently, used-tire collection, a vital measure in reducing mosquito breeding grounds.

Some government officials I speak with assure me that these issues have been quickly resolved – and indeed, both the managed-care companies and the sanitation contractors received payment for their services not long after going public. Nonetheless, these issues speak to a larger structural dysfunction that predates Zika or even Puerto Rico's mounting debt. For 64 years, Puerto Rico built its economy by offering itself as a tax haven for U.S. companies. While exploiting various tax incentives helped develop the island's physical and societal infrastructure, it was never meant to provide lasting economic stability. To the contrary, "We have multimillion-dollar companies whose money doesn't stay one day in Puerto Rico," says San Juan Mayor Carmen Yulin Cruz, who notes that more than $34 billion is taken out of Puerto Rico every year by U.S. corporations and sent to banks offshore. This has made Puerto Rico only more dependent on the U.S., preventing it from creating the sort of self-sustaining economic model that states on the mainland enjoy. And this, in turn, just further cripples its ability to deal with Zika.

While it waits for Congress to approve emergency-response funds, which could take months, given the summer recess, Puerto Rico has had to turn to private donations for things like condoms and insect repellent for its "Zika prevention kits." The New York Times recently reported that the CDC Foundation, a private charity that supports the work of the CDC, has raised only $1.7 million to stem the Zika epidemic worldwide, as opposed to the $55 million it raised for Ebola. Just the new mosquito traps, says Rullán, the island's former secretary of health, would cost Puerto Ricans $20 apiece. Each home needs three. "That's $60 million. Then you have to decide if you're going to treat septic tanks or water meters. And if you're going to use aerial larvicide, which requires helicopters – that costs billions."

A courtly, white-haired physician who was called out of retirement to advise Puerto Rico's governor on Zika, Rullán is frustrated, and with good reason. "Puerto Rico has the best chance of all to prove we can eliminate this disease, because we have the CDC right here, but you have to start now with a strategy that can be monitored until we get the job done."

At an international conference of experts in vector control, which took place in late May in San Juan, Rullán had a talk with the director of the Florida Keys Mosquito-Control District, which has 71 full-time and 39 part-time employees, and receives county funds. The Keys are home to more than 40 species of mosquito, including Aëdes aegypti. Recently, after one person came down with dengue, local officials deployed their entire mosquito-control infrastructure to contain the spread of the disease. Now, Rullán says, the Keys are similarly geared up for Zika, even though they have yet to have a confirmed case.

"They had five cases of dengue four years ago, and because of that, they have done aerial spraying and larvicide, they've done all the traps, they've done all these PSAs on how to do source reduction, and they've started to work on a six-month plan to reduce mosquitoes," he says. "We don't have any mosquito-control agency, but what we do have is about 30,000 cases of dengue a year, probably 85,000 cases of Zika, 139 pregnant women with Zika in their blood. And yet there's no vector-control plan, no public-service announcements and no funding, unless it starts appearing from wherever it appears. So how do you think I feel when I talk to the guy from Key West? It gets to a point where you go, 'Does Puerto Rico matter?'"

In talking to public-health officials like Frieden or Fauci, they are very careful to include Puerto Rico as part of the United States, though as Fauci tells me, "in terms of Zika, Puerto Rico is more like Brazil than it is the continental U.S." He is referring to the scale of the outbreak, but there is still something unspoken that makes it difficult to see Puerto Rico as just as "American" as Florida. "The entire way the U.S. has dealt with Zika in Puerto Rico says a lot about how the U.S. still views Puerto Rico," says Mayor Yulin, who is one of a number of Puerto Ricans who see the hidden hand of colonialism even in the government's refusal to help stop an epidemic.

"They don't see it, so it's not there," says Rullán. "But it is there. There is a huge ice mass just below the surface." He wonders when anyone will care.

"You just need a few babies born with microcephaly here in the continental U.S. for people to say, 'Why didn't you do anything?'" says Fauci. The current funding proposals in the House wouldn't give Puerto Rico nearly enough. "And that's a problem," he says.