On this hard hit tropical island, even the dead are getting pulled into the fight against Zika.
On a recent weekday, Roberto Barrera led a team of disease investigators into a graveyard in Caguas, a town about 20 miles south of San Juan. He shoved aside the heavy cement lid of an unused crypt and peered into the darkness. Instead of a coffin, he found about 4 feet of rancid water: a perfect breeding ground for the mosquitoes that carry the Zika virus.
“That’s not good,” he said, as he re-sealed the tomb.
In hot and humid Puerto Rico, the mosquitoes carrying Zika have found the perfect breeding ground. There have been 37,889 confirmed cases on the island, both homegrown and imported, according to Puerto Rico’s Health Department. Florida, by contrast, has 1,329 confirmed cases of Zika despite having six times the population — and only 262 two of them were locally acquired infections.
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And unlike the mainland, Puerto Rico rejected the widespread use of insecticides like naled to fight the menace, fearing their toll on people and the environment.
And that’s where Barrera’s team is stepping in. For the last several weeks, the Centers for Disease Control and Prevention has been working with the local government to turn this mid-sized city into a mosquito graveyard deadly enough to kill the spread of the Zika virus.
In the process, they’re making Caguas a test case for chemical-free Zika reduction.
At the heart of the effort are thousands of black 5-gallon buckets that have been modified to lure mosquitoes to their death. In the coming weeks, the CDC and Puerto Rican health authorities will be placing about 90,000 of these traps — called autocidal gravid ovitraps, or AGO traps — to cover 80 percent of the city’s center.
Whether the system is effective should become clear in the spring when wetter and warmer weather boosts the mosquito population.
Unlike other hard-hit areas, such as Brazil and Colombia, Zika has spread over the entirety of this 3,500-square-mile island and all of its 3.5 million residents are vulnerable, said Steve Waterman, the chief of the CDC’s dengue branch, who is overseeing Zika efforts here.
But it’s unclear if enough people have already been exposed to it — becoming immune to reinfection — that they’ll provide a human buffer once the mosquito-season resumes.
“The question is: Is there enough immunity — what we call herd immunity — for the transmission to really, really slow down?” he asked.
Scientists don’t know the answer to that yet. That’s why authorities are rushing to turn Caguas into an anti-insect fortress.
On a recent weekday, a small army of blue-clad workers were laying hundreds of AGO traps between the tombstones at Caguas’ cemetery. In the process, they were looking for pools of water often found in graveside flower vases or empty crypts, like the one Barrera examined, where mosquitoes might breed.
Getting the entire community — including the dead — to participate is critical, said Barrera, head of the CDC’s entomology and ecology activities and one of the trap’s inventors. The project aims to put three AGO traps in 30,000 homes. But a single noncompliant household can become a disease vector that ruins the efforts of an entire neighborhood, he said.
The system relies on creating a “constellation” of “sink holes” that will crash the mosquito population, he explained.
The buckets are a study in simplicity. Each one holds a few inches of water and fermenting hay that lures the Aedes aegypti in through a fist-sized opening at the top. A screen prevents the mosquito from reaching the water, and the insects get caught in sticky, non-toxic resin inside the opening. The traps cost about $11 each, and although they’ve been used to monitor mosquito populations in the past, they’re just now being considered eradication tools.
In smaller tests, the traps were able to reduce the mosquito population by 80 percent and the outbreak of mosquito-borne viruses by as much as 50 percent. But the AGO traps have never been implemented on this scale before.
And that’s why there’s so much interest in the project, said Waterman.
“There is a lot of effort in the entomology community to look for alternatives to insecticides,” he said.
Authorities in South Florida, for example, will be releasing genetically modified mosquitoes this year that are designed to produce offspring that die almost immediately. But not everyone is comfortable with the idea of mutant mosquitoes.
“The community has to understand why you release mosquitoes to kill mosquitoes,” Waterman said. “But it is a very promising [technology] that doesn’t involve insecticides.”
Despite the hemisphere’s Zika outbreak being more than a year old — the virus was first discovered in 1947 in Africa — there’s still much unknown about it.
While it has been linked to babies being born with abnormally small heads, there are suspicions it could be causing a host of other problems in infants exposed to the illness in the womb, from slowed growth to hearing loss to limb malformation. It also has been associated with Guillaine-Barré syndrome.
Puerto Rico has identified 3,018 pregnant women with Zika (in Florida, it’s 224) and 11 babies have already been born with virus-related defects. But because the virus peaked in August, doctors are bracing for a flood of new cases this year.
“Zika isn’t an on and off switch,” said Dr. Albert de la Vega, a San Juan-based obstetrician and gynecologist who has been studying Zika-related birth defects. “There’s a range of problems it might cause that aren’t so easy to detect.”
“There are babies being born who look perfectly fine but they’re not,” he added. “And we may not even find out for years.”
The outbreak has been particularly cruel in a country struggling under a $70 billion debt that has crippled its ability to tackle the health crisis. Doctors are in short supply and some hospitals are barely surviving. Unlike U.S. states, Puerto Rico, a commonwealth, receives a fixed amount of Medicaid funding every year, regardless of actual Medicaid costs. And authorities complain that’s hammering the sector.
“We have a health department that is extremely weak,” said Nabal Bracero, the founder of PROgyn, a non-profit that provides healthcare and education to women. “And we’re at a moment in time where we need all the help we can get.”
And with the waves of Puerto Ricans heading to the U.S., it’s no longer appropriate to think of Zika as an isolated problem.
“If we don’t treat our Zika problems here, our problem is going to become the problem for the entire [U.S.] East Coast,” he said.
Rita Alvarado, a 58-year-old retired teacher, had a bout of another mosquito-transmitted virus, chikungunya, last year that was so severe she couldn’t drive for a month and had to be helped to the bathroom. As workers placed the bucket-traps in her home recently, she said she’s relying on prevention and prayer to avoid the new virus.
“If these traps can stop Zika, then it’s very good,” she said. “But I’ve also been saying, ‘Oh Lord, please don’t give me Zika.’”