MIAMI-Donated blood should be tested for the Zika virus, which can cause birth defects, US regulators warned amid a mounting outbreak of the mosquito-borne disease in the United States.
The move announced Friday revises a previous Food and Drug Administration guideline issued in February that recommended active screening of donated blood only in "areas with active Zika virus transmission."
Since there is "still much uncertainty regarding the nature and extent of Zika virus transmission," the recommendation for testing all donated blood "will help ensure that safe blood is available" for everyone, said Peter Marks, director of the FDA's Center for Biologics Evaluation and Research.
Stricter national safeguards are needed as evidence has emerged that Zika can be transmitted sexually, and that those infected often show no symptoms, the FDA said.
More than 2,500 people in the United States have been diagnosed with Zika, along with more than 9,000 in the US territories such as Puerto Rico, according to the US Centers for Disease Control and Prevention.
Most of those cases were brought in by people infected while traveling abroad.
There are 584 pregnant women on the US mainland with lab evidence of Zika infection, and 812 in the US territories.
Florida in July announced its first cases of locally transmitted Zika, with 42 infections.
Donated blood is already being tested in Florida and Puerto Rico, and at least one unit of blood in Florida was found to contain the Zika virus and was intercepted, Marks told reporters on a conference call.
An expanded blood supply testing "will be in effect until the risk of transfusion transmission of Zika virus is reduced," said the FDA.
President Barack Obama on Saturday called on Republicans, who control both chambers of the US Congress, to allocate more money to fight the spread of Zika.
In February "I asked Congress for the emergency resources that public health experts say we need to combat Zika," Obama said in his weekly radio address.
"That includes things like mosquito control, tracking the spread of the virus, accelerating new diagnostic tests and vaccines, and monitoring women and babies with the virus."
Republicans in Congress however "said no." Instead resources used to fight Ebola, cancer and other diseases were re-directed towards Zika.
"But that's not a sustainable solution," Obama said. The delay for more funds "puts more Americans at risk."
Congress "should treat Zika like the threat that it is" and "fully fund our Zika response. A fraction of the funding won't get the job done. You can't solve a fraction of a disease," he said.
Zika is primarily spread by the bite of an Aedes aegypti mosquito, but it can also be transmitted sexually.
On Friday, US authorities announced the first known case of a man who had Zika but did not know because he showed no symptoms - and then subsequently infected his female partner during unprotected sex.
Four out of five people who get Zika do not show any of the common symptoms, which may include fever, rash, joint pain and red eyes.
"As new scientific and epidemiological information regarding Zika virus has become available, it's clear that additional precautionary measures are necessary," said Luciana Borio, the FDA's acting chief scientist.
The World Health Organization says 53 countries around the world have reported Zika outbreaks since 2015.
Two US lawmakers, Congresswoman Rosa DeLauro of Connecticut and Congressman Lloyd Doggett of Texas, had recently urged the FDA to expand testing for Zika to blood banks nationwide, saying it would cost less than $10 per donor.
On Friday, DeLauro applauded to decision to recommend testing, calling it "a strong step forward in protecting our nation's blood supply and the American people."