WEDNESDAY, Feb. 10, 2016 (HealthDay News) -- Traces of the Zika virus have been identified in the tissue of two babies who died in Brazil from a birth defect marked by underdeveloped heads and brains, U.S. health officials said Wednesday.
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 mosquito-borne pathogen may be to blame, Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, 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 on behalf of 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 -- has prompted health officials to warn pregnant women or those thinking of becoming pregnant to take precautions or consider delaying pregnancy.
And the CDC is recommending that pregnant women avoid the regions of Central and South America and the Caribbean, where Zika virus has been identified and officials have described it as spreading "explosively."
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 funding request followed a WHO emergency declaration last week that the Zika virus is now a global health threat, based on the suspicion that the virus may be to blame for the thousands of birth defects in Brazil in the past year.
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.
The CDC advisory followed a report out of Texas that one confirmed case of Zika virus infection was transmitted through sex, not a mosquito bite.
The Dallas County Health and Human Services Department reported last week that an unidentified patient had become infected with the Zika virus after having sex with an individual who had returned from Venezuela, one of the Latin American countries where Zika is circulating.
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.
The U.S. blood supply is also being monitored closely. The American Red Cross on Feb. 3 asked potential blood donors who have traveled to areas where Zika infection is active to wait 28 days before giving blood.
The chances of Zika-infected blood donations remain extremely low in the United States, Dr. Susan Stramer, vice president of scientific affairs at the American Red Cross, said in a statement at the time.
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 Associated Press reported.
Over the weekend, a small ray of hope emerged in Colombia. Although 3,177 pregnant women in that country have been diagnosed with the Zika virus, President Juan Manuel Santos said there's no evidence the virus has caused any cases of the birth defect, according to the AP.
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.