Officials in the southwestern state of Texas have reported what may be the first case of the Zika virus being transmitted in the United States by sexual contact.

On Tuesday, health officials in Dallas County said the person became infected after having sexual contact with a person who had returned from Venezuela. Venezuela is a country where the virus is present.

The Centers for Disease Control and Prevention, the federal U.S. health agency, confirmed the infection in an email to VOA. The CDC wrote that it "confirmed through laboratory testing the first U.S. case of Zika virus infection in a non-traveler in the continental United States."

On its website, the CDC notes "Zika virus is transmitted to people primarily through the bite of an infected Aedes-species mosquito." But it says "the spread of the virus through blood transfusion and sexual contact have been reported."

Last year, French scientists reported the virus was found in the semen of a patient during the 2013 Zika virus outbreak in French Polynesia. This supports the possibility that the virus can be transmitted sexually.

Dr. Tom Frieden is the head of the CDC. He also sent out Tweets to confirm the infection.

Brazil reported the first case of Zika virus in this latest outbreak in May 2015. Since then, the virus has spread by mosquitoes and has caused infections in Brazil, many Latin America countries, and the United States.

With the Summer Olympics taking place later this year, Brazilian President Dilma Rousseff said her government would spend whatever is necessary to kill the kind of mosquitos that carry the virus.

In a speech, she said, "my entire government is working on fighting this emergency. There will be no lack of funding, and I'm certain that I will be able to count on the Congress' support."

She said she has spoken with President Barack Obama about the virus. She said Brazil will work with the U.S. government "to establish our capacity and improve it in order to develop as quickly as possible a vaccine for the Zika virus."

On Monday, the World Health Organization declared the Zika virus a global public health emergency. It says four million more people could be infected by the end of the year.

The health agency called for more international resources to fight the spread of Zika but ruled out a ban on traveling or trade. And the International Red Cross is calling for $2.3 million in emergency money to fight Zika in Latin America.

I'm Anna Matteo.  

VOANews reported this story. Christopher Jones-Cruise adapted it for VOA Learning English. Hai Do was the editor.