RECIFE, Brazil -- There was a worrying development on Tuesday in the Zika virus outbreak.
A person in Dallas, Texas, was infected after sex with a partner who had been in Venezuela where Zika is an epidemic.
Zika is most often transmitted by mosquitoes. It's suspected of causing devastating birth defects. Brazil is the hardest hit.
It's a search and destroy mission by government workers. Each morning, teams of Army and health workers target neighborhoods in the city of Recife, Brazil, looking to kill mosquitoes that may carry the Zika virus.
Recife is the epicenter of an explosion of microcephaly -- an abnormally small head at birth -- linked to the infection. Dr. Jailson Correia heads up the city's Health Department.
"What I'm expecting now is to reduce the population of mosquitoes to see less Zika infection in 2016 and hopefully less microcephaly cases later on," he said.
There are 72,000 homes in this district alone and officials follow-up every two months.
Thirty-year-old Silvania Borges is pregnant with her fourth child.
A worker added a chemical to kill mosquito larvae in a water storage tank at her house. The majority of mosquito breeding occurs in people's homes.
What is she doing at home to lower her chance of getting bitten by a mosquito?
Borges told CBS News she tries to keep her home clean, eliminates standing water and occasionally uses bug spray. Still, she gets mosquito bites about once a week. She's had no obvious symptoms of Zika, but 80 percent of the time, those infected don't feel sick.
She told CBS News she is worried about her baby.
"Prejudice exists and is serious. As a mom, I would give all my love, but I would worry about the outside world," she said in Spanish.
CBS News asked Dr. Correia about Tuesday's report of sexual transmission of Zika virus in the U.S. He said that has not been reported yet in Brazil, but that officials are sure to take a closer look now.