BROWNSVILLE, Texas – If the Zika virus were to spread through the USA, it could very well start here: a busy border city where thousands of people cross each day between the U.S. and Mexico, where the mosquito that transports the virus is found in abundance, and where poorer neighborhoods could foster its spread.
Zika is already spreading through Mexico, but Texas may have two big advantages over its southern neighbor: the simple window screen and an abundance of air conditioning.
As of Friday, Mexico had tallied 272 cases of Zika, with most of them occurring in the southern states of Chiapas and Oaxaca, according to the office of Mexico’s Health Secretary. Health officials have recorded 31 people in Texas infected with the Zika virus — all contracted outside the USA.
State and local health officials here expect a homegrown outbreak eventually, especially in border cities like Brownsville and the surrounding area of Cameron County. How widespread it will be depends on whether residents heed the advice of the expects and take preventive measures, officials said.
“It’s not a matter of if it’s going to happen,” said Esmeralda Guajardo, Cameron County’s health administrator. “It’s a matter of when.”
The Zika virus, transmitted largely by the Aedes aegypti mosquito, has spread through 44 countries since first surfacing last year. In the USA, the Centers for Disease Control and Prevention reports 472 travel-associated cases of Zika as of May 4. None were acquired locally through mosquito bites. Zika causes symptoms such as fever, rashes and joint pain and in pregnant women can result in babies born with a serious birth defect, microcephaly, where babies’ heads are much smaller than normal.
The Aedes aegypti mosquito is common along the Gulf Coast, especially in South Texas and along the border, said Sonja Swiger, an entomologist with the Texas A&M AgriLife Research and Extension Center at Stephenville. Unlike other breeds of mosquitoes that feed on one human until they’re gorged with blood, the female Aedes will extract smaller portions from several humans, raising the risk of infection and outbreak, she said.
They’re the same mosquitoes that transmit dengue fever and chikungunya, and, more than 150 years ago, were the main culprits in the 1853 yellow fever outbreak in New Orleans that killed nearly 8,000 people.
“She’s a sneaky little bugger,” said Swiger. “They’re excellent carriers and transmitters … Not all insects are good at that. This one is very well established.”
Dr. John Hellerstedt, the state health commissioner, said he is preparing for outbreaks throughout in Texas, but the 1,254-mile border with Mexico is of particular concern. Last month, he travelled to Laredo to meet with health officials from both sides of the border to review response plans.
The massive flow of people across the border each day may elevate the risk, but everyday items found more commonly on the Texas side, such as window screens and air conditioning units, help reduce the Zika threat here, he said.
“The best way to combat it is prevention,” Hellerstedt said. “These simple things can be very effective.”
In 2013, screens and a/c units helped contain a dengue outbreak that spread quickly through South Texas. When the first case surfaced in Cameron County, officials, with CDC’s help, dispatched workers who fanned out in a one-mile radius from the infected person’s house, knocking door to door, assessing properties, draining birdbaths and other standing water where mosquitoes breed, and making sure the virus didn’t spread. It worked: For the year, Cameron County saw around 37 total cases of dengue, of which only 21 were acquired locally, according to the Texas Department of State Health Services.
“It was seen as a success,” Guajardo said. “That’s pretty much the same model we’re going to use should a Zika case be reported locally.”
Currently, health officials here are reviewing response plans and urging residents to take simple steps to reduce mosquito breeding, such as dumping out water that pools in tires or flower pots outside. In places like Brownsville, the task of spreading that message has fallen largely to promotoras, or trained community educators who speak Spanish and help residents with a variety of things, ranging from nutrition to family planning and stress management.
Last month, the dozen promotoras at the Proyecto Juan Diego community center here underwent a three-hour, state-led training program detailing the threats of Zika and how to best prevent its spread. Each day, they bring that message to the homes of residents, along with bilingual pamphlets.
“People are aware of it but, until it shows up here, it’s a hard thing to put their attention on it,” said Sister Phylis Peters, the center’s director and a member of the Daughters of Charity Catholic organization. “There are so many other things. They’re just trying to survive.”
County officials are also dispatching sprayers — machines mounted on the back of pickup trucks that spray pesticides into the air — several times a week in neighborhoods where mosquitoes have been spotted, and finalizing plans for an outbreak, Guajardo said.
But such spraying, effective on the Culex mosquito, may not be enough to tamp down on the Aedes aegypti.
“We cannot spray our way out of this,” said Umair Shah, executive director of Harris County, Texas, Public Health and Environmental Services, at a national summit on Zika preparedness in April.
At a meeting last week of county and local heath and code enforcement officials, Gustavo Olivares, Cameron County’s environmental health director, offered the attendees more mosquito traps and went over the procedure of what to do if a case surfaces.
He urged everyone in the room to stay vigilant.
“The more we look for it, we’re going to find it. I guarantee it,” Olivares said. “It’s not just about finding it: It’s about finding it and taking action before it becomes a problem.”