Houston Is Still at Risk of a Zika Outbreak

Summer is returning to Houston, bringing heat, humidity and fresh fears about mosquito-borne illnesses like Zika. From late spring to early fall, Houston offers an ideal climate for mosquitoes. The notorious aedes aegypti species can carry nasty diseases like Zika, chikungunya and dengue fever.

Experts say it’s almost impossible to know how bad Zika will be in Houston this year, or whether the city will experience a similar outbreak. There are just too many factors — most notably, whether local mosquitoes pick up the infection.

Texas had 312 confirmed cases of Zika in 2016, according to the Centers for Disease Control and Prevention. The agency estimates six of those cases were locally transmitted — meaning the infected person had neither left the country nor had sex with someone who had.

Those local cases come from the Rio Grande Valley, which had a small outbreak last year. In April, Texas put out a Zika warning for six counties that border Mexico: Cameron, Hidalgo, Starr, Webb, Willacy and Zapata.

At least for now, Houston-area mosquitoes don’t appear to be infected. All 35 of the city’s confirmed Zika cases have been in people who’d traveled to Central America, South America or the Caribbean. Dr. Umair Shah, executive director of Harris County Public Health, said he tests about a million mosquitoes per year. None have been positive for Zika — although the county can only test a fraction of the insects that live here.

“This is a needle in a haystack,” Shah said. “There’s no way we can test every mosquito in Harris County. That would be trillions of mosquitoes.”

Just in case, he said, Houstonians should take precautions. These include wearing long clothes, making sure windows and doors are sealed, draining puddles of standing water and using a DEET bug repellent.

Residents should also educate themselves on the signs of Zika, which causes flu-like symptoms, he said. Anyone with Zika should wear condoms during sex. And he or she should take extra precautions against getting bitten for at least three weeks, so mosquitoes won’t catch the virus and spread it to other people.

If a Zika outbreak does occur in Houston, the city will be uniquely equipped to deal with it. Harris County Public Health has been gassing mosquitoes since the 1960s, when voters approved a mosquito control division. But preventing an outbreak would still require personal responsibility, Shah said. The aedes aegypti mosquito is active during the daytime, making it less vulnerable to evening sprays.

Nikos Vasilakis, a professor who studies mosquito-born illnesses at University of Texas Medical Branch, said Houston was a “shining star” with regards to mosquito-control efforts. But when asked why Houston hasn’t had a Zika outbreak, he said it was mostly luck.

“The risk is high,” Vasilakis said. “Why we don’t see it is a million-dollar question.”

If Houston does have an outbreak, he explained, it will start in the city’s poorer neighborhoods, where there are fewer public services and more places for mosquitoes to breed. From there, infected humans would spread it across the city. Vasilakis said he does not think a Texas outbreak would be as bad as the ones we’ve seen in Central America. That’s because Americans are “antisocial,” he said. They spend less time outside with friends and more time sealed in air-conditioned homes and workplaces.

Still, he thinks state and federal governments should take a proactive approach, earmarking more funding for control, prevention and awareness before the problem gets out of hand. And in the absence of well-funded women’s health care, he worried pregnant women were getting a caricatured image of the dangers of Zika.

Media coverage of Zika often focuses on microcephaly — the ailment that produces small heads and brains in babies. It shows up in only 1 to 10 percent of infants, Vasilakis said.

“The effects of Zika are going to be shown many years later, in epilepsy and cognitive abnormalities,” he said. “That is the real cost of a Zika infection.”

This article appears in Summer Guide 2017.