HOUSTON (CN) - Zika has made its way to Texas carried by three people who recently visited Latin America and tested positive for the virus, according to Harris County health officials.
Harris County Public Health & Environmental Services confirmed the three cases Monday, bringing the total to seven confirmed human cases in the state's most populous county.
"The individuals developed symptoms that are often associated with the Zika virus, which include fever, rash, joint pain. All individuals have since recovered," the agency said in a statement.
The latest three diagnoses include a middle-aged woman, a young man and a boy under age 10, all of whom traveled separately to El Salvador and developed symptoms in November or December, the Houston Press reported.
The agency's executive director Dr. Umair Shah said the news is cause for concern but not panic because so far the only reported cases are in travelers, which likely means Texas mosquitoes aren't yet carrying the virus.
But with scientists reporting Zika is to blame for 3,000 babies born with microcephaly in Brazil in 2015, alarm is spreading.
Babies with microcephaly are born with abnormally small heads. It may also cause developmental delays and seizures.
The World Health Organization declared Zika a public health emergency on Monday, and estimates the virus will spread throughout the Western Hemisphere and infect up to 4 million people by 2017. Zika is transmitted by the Aedes mosquito, which inhabits warm climates throughout the Western Hemisphere, and can only catch the virus by biting an infected human.
"This is the same mosquito that transmits dengue, chikungunya and yellow fever," according to the WHO.
The link between Zika and microcephaly has not yet been proven, but Brazilian activists are already pressing the government to allow abortions in such cases, the BBC reported.
Brazil permits abortions if the pregnancy endangers the mother, or is caused by rape. If an abortion is done outside these parameters, the woman can be sentenced to up to three years in prison.
Shah, the Harris County health director, said he expects more Zika cases in Texas as people travel to and from Latin America.
His agency urged travelers to stay in hotels with air conditioning, screens, windows and doors and to wear insect repellant along with long-sleeved shirts and pants.
The agency also advised parents of infants to put mosquito netting over cribs, strollers and baby carriers.
Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston, cautioned that although it's possible the Zika virus in mosquitoes will not reach the Gulf Coast in 2016, poor pregnant women are especially at risk.
"The important factor of poverty promotes greater mosquito exposure to people who live in inadequate housing without screens or central air conditioning, or live next to degraded environments with trash and standing water that allow mosquitoes to breed," Hotez wrote in a letter published Sunday by the Houston Chronicle.
There is no vaccine for the virus.
Researchers first identified the virus in rhesus monkeys in Uganda in 1947. Five years later, people in Uganda and Tanzania tested positive for the virus.
"Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific," the WHO said.
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