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IAMI — Dr. Christine Curry has been talking with her pregnant patients about the Zika virus for months, asking them where they have traveled and advising them on how to avoid mosquito bites. On Friday, the Miami obstetrician-gynecologist brought in another tool: a map on her cell phone showing one square mile of the city where officials believe mosquitoes have spread the virus — a first in the continental United States.

“I saw 30 pregnant women today, so I had 30 conversations about Zika,” Curry said Friday, the day officials announced that four recent Zika cases in this area were almost certainly the result of locally infected mosquitoes.

The four people — three men and a woman — were infected with the virus in early July, and it is possible that other cases could come to light, officials said. But even if this cycle of spread has ended, it foreshadows the small bursts of Zika transmission that officials said could continue to pop up in the coming months, most likely in states along the Gulf Coast, like Florida, where the mosquitoes that transmit the virus thrive during the hot and humid summer.

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For Curry and other clinicians, the announcement drove home the point that pregnant women here are at risk, albeit a small one. Sure enough, one patient Curry saw Friday lived in the area where disease detectives believe transmission occurred.

Curry, an assistant professor at Jackson Memorial Hospital and the University of Miami, said she has encouraged her patients to protect themselves but avoid panicking. She told one patient, no, she didn’t need to move to New York for the rest of her pregnancy. But she has also nudged other patients to consider if they really need to be the ones in the family to walk the dog along the Miami River.

“It’s that fine balance where, ‘I need you to be worried enough where you change your behavior, but not so worried that you’re paralyzed,’” Curry said. “It’s that sweet spot between frightened and actionable.”

The area of focus sits just north of downtown Miami in Wynwood, a hip and gentrifying neighborhood famous for its vibrant, eye-catching graffiti murals on many buildings, from the corner convenience store to the contemporary art galleries.

Parts of this area feel desolate, with boarded-up buildings and homeless people seeking out the small pockets of shade. But it also has a bustling stretch of boutiques, bars, and restaurants touting their local ingredients and craft beer selection. A farmers market Saturday featured a live jazz band and stands selling $6 coconut water and homemade organic dog treats.

The neighborhood was crowded throughout the day Saturday. Many people said they had not heard the Zika news, but most did not seem fazed when told. It was too hot to wear long pants and sleeves and, in their minds, what good would bug sprays do.

It’s South Florida, they said. You’re going to get bitten by mosquitoes.

“I’m not worried because I’m not pregnant,” Brittney Williams, 25, said as she and friends were preparing to drive to the beach. They were wearing T-shirts or tank tops, and shorts or skirts, the standard uniform as the temperature pushed past 90.

Indeed, health officials say their top priority is protecting pregnant women because the virus can pass from them to their fetuses, causing devastating birth defects. Officials have not said whether the woman in the group of four people infected locally is pregnant.

Since officials in Florida started investigating the local cases, they have handed out more than 4,000 Zika prevention kits to pregnant women in Miami-Dade County and adjacent Broward County, where some of the individuals suspected of being infected in Wynwood live. The kits include tablets that kill mosquito larvae where water collects, mosquito repellant, and condoms because Zika can be spread through sex.

For most people, though, a Zika infection will cause no symptoms or just a few days of fever, rash, and body aches, although it can, in rare cases, cause a form of temporary paralysis.

Dr. Nicole Iovine, an infectious disease physician at the University of Florida in Gainesville, said her hospital has treated a number of people who contracted the virus while traveling, but that no one has had to be admitted. None of the four people infected in the Miami area was admitted to hospitals either, Florida Governor Rick Scott said Friday.

“It’s that mild of an illness,” Iovine said.

In the Wynwood area, the cranes dotting the skyline may be building high-end apartments — a banner on one of several condo towers under construction blared that its penthouses started at $699,000 — but what’s going on at street level is a different story, and hints at why mosquitoes in this area could have transmitted Zika.

Miami trash heap
Despite gentrification, parts of Wynwood still feels desolate. And improperly disposed trash can provide excellent breeding sites for the mosquitoes that spread the Zika virus. Andrew Joseph/STAT

Despite the changes in the neighborhood, there are still plenty of empty lots, some of which are littered with empty beer bottles and soda cans. The primary driver of the Zika virus, the Aedes aegypti mosquito, lays its eggs in man-made containers that collect water, and can even make do with an improperly disposed bottle cap.

The overgrown grass on some of the properties can provide cover for the mosquitoes from stepped-up spraying campaigns. And the open dumpsters at the construction sites, filled with building materials and plastic tarps, provide plenty of nooks and crannies for water to pool and mosquito larvae to bloom.

Saturday was dry, but rain was in the forecast for the next several days.

“It’s perfect conditions,” said John Beier, a vector biologist at the University of Miami. “It’s raining every couple days. High temperatures, high humidity. Of all the times during the year, this can be considered the high point for mosquitoes.”

More mosquitoes buzzing around increases the chance that some of them will take a blood meal from a person who contracted the virus while traveling in a Zika-affected area. After a few days, the mosquitoes become infectious themselves and can pass the virus to other people they bite.

Experts have been on the lookout for local spread of Zika in the Miami area because it is a hub of travel to and from Latin America and the Caribbean, regions where the virus has spread explosively. As of Friday, Miami-Dade County had at least 99 travel-related Zika cases, almost double what any other county in the state has seen.

The county’s mosquito abatement crews were out in Wynwood Saturday, going door to door with backpack sprayers and larvicide tablets and dumping out containers of standing water. Agencies have launched a more aggressive control effort since signs of local spread first emerged, and have been passing out educational information in English, Spanish, and Creole and trapping and testing Aedes mosquitoes for Zika.

Officials say finding a mosquito with Zika would be the smoking gun to confirm local spread was occurring, but liken the chances of that to finding a needle in a haystack.

Kat, a Wynwood resident who asked to be identified by her first name to protect her family’s privacy, said Saturday that her backyard had just been sprayed that morning. She said she was keeping her four children inside for the next few days until health officials knew whether mosquitoes in the area were still spreading Zika.

“Four cases?” she said. “That’s a lot. One’s too many for me.”

Dr. Tom Frieden, the director of the Centers for Disease Control and Prevention, said Friday that the agency was not recommending that pregnant women stay away from Miami. But he said that could change if other people in the area contract infections even with the ramped up mosquito-control campaign.

Aedes ageypti mosquitoes live for only a few weeks, so those that were infectious in early July and bit the four individuals are probably dead. It would take other mosquitoes becoming infectious for the virus to spread anew, experts said.

“In all likelihood, they’ve gone to see Elvis,” said Joseph Conlon, a retired Navy entomologist and technical advisor to the American Mosquito Control Association.

Florida is one of the few places on the US mainland that has experienced local cases of dengue and chikungunya, viruses related to Zika that are also spread by Aedes aegypti mosquitoes. But those outbreaks have affected only small numbers of people and have been quickly contained, a pattern that experts believe will hold with any Zika clusters here. People in the continental United States have much less exposure to mosquitoes than other areas thanks to air conditioning and screened windows.

Still, the news that local transmission had occurred after months of warning pushed the sweeping outbreak to a new phase. Margarita Vega, a nurse and site manager at a health center run by the nonprofit Community Health of South Florida, said clinicians there had been keeping an eye out for Zika and educating patients about the virus for months.

“Now,” she said, “it hits home.”

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