DALLAS, Feb. 2 (UPI) -- One day after the World Health Organization declared an international health emergency due to a spread of the Zika virus, the first two cases were reported in the United States, officials said Tuesday.
Dallas County health officials said one of the patients contracted Zika through sexual contact with a person who had picked up the virus in one of the countries the WHO says it has spread to.
In the second case, the affected person recently traveled to Venezuela and brought the virus back to Texas, officials said.
Humans pick up the Zika virus from mosquitoes, the Centers for Disease Control and Prevention has said. From there, it can also be transmitted to another person through various forms of contact, including sexual.
"It raises the awareness that Zika can be transmitted from mosquito to human, humans to mosquitos, and now we know through sexual transmission," Dallas County health director Zachary Thompson said.
The WHO's primary concern about the virus is its possible link to microcephaly -- a condition that results in brain damage and smaller-than-normal head sizes in newborn babies. The link is not definitive, but it is suspected among global health experts.
Monday, the WHO declared an international health emergency after the virus spread to about two dozen countries, mostly in Latin America.
CDC Director Tom Frieden said two groups at the greatest risk of picking up Zika are those in South and Central America and the Caribbean, and pregnant women. The virus's spread has been particularly substantial in Brazil.
Dallas officials said at least one of the two unidentified patients, though, is not a pregnant woman -- meaning they will experience only cold-like symptoms or none at all.