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Blood from the continental United States is being shipped to Puerto Rico to stem the possibility of the Zika virus spreading through blood transfusions, federal officials announced Monday.

The first shipment of blood products arrived Saturday in Puerto Rico, where experts say an estimated 1 in 5 residents could be infected with Zika this year.

Although the virus is primarily spread through mosquitoes, officials with the US Department of Health and Human Services said they believe Zika can also be spread through blood products, particularly because reliable tests to screen for the virus are not available yet. The blood being brought into Puerto Rico will only come from places in the United States without active transmission of the virus.


In the continental United States, the only documented cases of Zika, so far, have occurred in residents who contracted the virus while traveling abroad and in a handful of instances in which men who, became infected while traveling, transmitted the virus to sex partners.

When contracted, the virus can cause a few days of fever, rash, and head and body aches, although most people won’t even show symptoms. Still, global health officials increasingly believe that pregnant women who contract Zika face higher risks of having babies with severe birth defects, including underdeveloped brains and abnormally small heads, a condition called microcephaly.


The US Food and Drug Administration last month issued guidelines to protect the country’s blood supply, including by asking people who returned from places where the virus is spreading to delay giving blood for four weeks.

Where you live can help determine whether you're at risk of contracting Zika. Alex Hogan/STAT