THURSDAY, Feb. 11, 2016 (HealthDay News) -- U.S. health officials are shipping test kits for the Zika virus to health departments around the country. They are to be used by pregnant women returning from Latin America and the Caribbean, where the virus may be to blame for severe birth defects.
The U.S. Centers for Disease Control and Prevention is also recommending that pregnant women avoid those regions of Central and South America and the Caribbean where Zika virus has been identified and officials have described it as spreading "explosively."
So far, the epidemic has seemingly been limited to Brazil. It is suspected -- but not proven -- that the virus is to blame for a birth defect called microcephaly that causes babies to be born with abnormally small heads and possible brain damage.
The CDC is telling doctors to test the women for Zika infection between two weeks and 12 weeks after they return home. Those thought to have been infected could then have ultrasound scans to monitor their fetus' development.
The CDC's director, Dr. Tom Frieden, said Thursday that the agency has shipped about 12,000 of 62,000 available Zika tests to health departments in three dozen states and is working to produce 30,000 more tests.
The CDC has said it does not expect the Zika virus, which is transmitted by mosquito bites, to become widespread in the United States.
On Wednesday, U.S. health officials reported that traces of the Zika virus had been identified in the tissue of two babies who died in Brazil from microcephaly.
The discovery doesn't prove the Zika virus is the cause of thousands of cases of microcephaly in Brazilian babies since the spring. But, it's the firmest connection yet that the pathogen may be to blame, Frieden told a Congressional panel, USA Today reported.
"This is the strongest evidence to date that Zika is the cause of microcephaly," Frieden told the House Foreign Affairs Committee. But, he added, more tests are needed to confirm that the Zika virus is the cause of the birth defect.
Frieden and Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, appeared before the panel to lobby for President Barack Obama's request for $1.8 billion in emergency funds from Congress to combat the threat of Zika virus.
The Zika virus was first identified in Uganda in 1947, and until last year was not thought to pose serious health risks. In fact, approximately 80 percent of people who become infected never experience symptoms.
But the increase of cases and birth defects in Brazil in the past year -- suspected to exceed more than 4,100, making that nation the epicenter of the epidemic -- has prompted health officials there to warn pregnant women or those thinking of becoming pregnant to take precautions or consider delaying pregnancy.
On Thursday, it was reported that two American women who had contracted the Zika virus while traveling abroad had miscarried after returning home. The virus was found in their placentas, according to a CDC spokesman, the Washington Post reported.
This is the first time that U.S. health officials have reported miscarriages in American women who had become infected while traveling abroad, although there have been many miscarriages reported in Brazil, the newspaper said.
Also Thursday, Brazilian health officials said they had entered into an agreement with the University of Texas to develop a Zika vaccine, with the hope that it would be ready for clinical testing within a year, the Associated Press reported.
Since the Zika epidemic first surfaced in Brazil last spring, the virus has spread to 30 countries and territories in Latin America and the Caribbean. The World Health Organization (WHO) now estimates there could be up to 4 million cases of Zika in the Americas in the next year.
The Obama administration's request for funding, made Monday, would allow for an expansion of mosquito-control programs, speed development of a vaccine, develop diagnostic tests and improve support for low-income pregnant women.
The earliest a vaccine could be developed would be some time next year, Fauci has said.
The White House's $1.8 billion funding request followed a WHO emergency declaration last week that the Zika virus is now a global health threat.
The Obama administration action also followed a new advisory from the CDC that pregnant women with a male sex partner who has traveled to, or lives in, an area affected by active Zika virus transmission should refrain from sex or use condoms until the pregnancy is over.
The CDC said the precaution is in place "until we know more" about the dangers of sexual transmission of the virus.
Scientists have suspected that Zika could be transmitted sexually, and there have been scattered reports of similar occurrences in recent years.
If research proves that the virus can be spread through sex, it could complicate efforts to contain infections from the virus.
According to the White House, the CDC had reported 50 laboratory-confirmed cases among U.S. travelers from December 2015 through Feb. 5, 2016. There has so far been no transmission of the Zika virus by mosquitoes within the United States. But, some Americans have returned to the United States with infections from affected countries in South America, Central America, the Caribbean and the Pacific Islands, the AP reported.
For more on Zika virus, visit the U.S. Centers for Disease Control and Prevention.
To see the CDC list of sites where Zika virus is active and may pose a threat to pregnant women, click here.