Zika Virus Outbreak Updates: Dallas Case Spotlights Sexual Transmission

— -- As the Zika virus outbreak continues, including in wide swaths of Central and South America, concerns are growing, especially for pregnant women because the mosquito-borne virus has been linked with a serious birth defect called microcephaly, characterized by an abnormally small head and brain.

Here are the latest updates to what the World Health Organization is now calling a global health emergency.

CDC to Release New Guidelines After Sexually Transmitted Zika Virus Found in Dallas

A case of sexually transmitted Zika virus in the U.S. was confirmed Tuesday by the U.S. Centers for Disease Control and Prevention.

This is the first time in this current outbreak that the virus has been reported to have been transferred by sexual contact in the U.S. Normally the virus cannot spread from person to person and is usually transmitted via infected mosquitoes.

The Dallas Department of Health and Human Services reported that an infected traveler returned from a country with Zika transmission and infected a partner with the virus.

Officials from the CDC said in a statement that they "will issue guidance in the coming days on prevention of sexual transmission of Zika virus, with a focus on the male sexual partners of women who are or who may be pregnant."

The CDC is now warning women who may become pregnant to consult their health care provider if their partner had exposure to the Zika virus and pregnant women should avoid exposure to semen from someone who had been exposed to the virus.

American Red Cross Asks Blood Donors to Wait 28 Days After Visiting Zika Areas

The American Red Cross is asking that anyone returning from a country with ongoing Zika transmission to wait 28 days before donating blood.

The American Red Cross is implementing the "self-deferral" as the Zika virus continues to spread across the Americas. The organization is also asking that anyone who develops symptoms in 14 days after donation to contact the blood center so the blood can be quarantined.

“The American Red Cross is dedicated to providing the safest, most reliable blood products possible to patients in need," said Dr. Susan Stramer, vice president of Scientific Affairs at the American Red Cross. "We are closely monitoring the spread of Zika virus."

There are at Least 48 People Infected in the U.S.

There are at least 48 people infected with the Zika virus. Nearly all -- except in the sexually transmitted case mentioned above -- are believed to have been contracted outside of the U.S.

Those infected are spread across 12 states, though the most cases have been found in Texas, with eight reported cases in that state.

Additionally, in Puerto Rico, where the ongoing Zika virus transmission is occurring, there are at least 20 people confirmed infected with the virus.

What Does the Virus Do?

Common symptoms of the Zika virus include fever, rash, joint pain and conjunctivitis, according to the CDC. Approximately one in five people infected with the virus show symptoms. Severe complications from the virus that require hospitalization are rare, according to the CDC.

The virus has also been associated with a rise of microcephaly birth defects in which an infant is born with an abnormally small head, which can cause significant developmental delays.

The CDC is also investigating if a rare paralysis syndrome called Guillain-Barre is related to the virus. The syndrome is an immunological reaction that can also occur after other viral or bacterial infections.