The Food and Drug Administration said Tuesday that anyone infected by -- or potentially exposed to -- the Zika virus should wait at least four weeks before donating blood in the United States. The agency said that includes individuals who have recently traveled to Zika-affected regions, those who have had symptoms suggestive of a Zika infection in the past month, as well as those who have had sex with a person who has traveled to or lived in Zika-affected areas in the previous three months.
In addition, the FDA said that in areas where there is active Zika virus transmission -- which includes U.S. territories such as Puerto Rico, U.S. Virgin Islands and American Samoa -- blood used for transfusions should be obtained from areas of the country where the virus isn't present. People living in those affected areas also should consider refraining from giving blood, the agency said.
"Based on the best available evidence, we believe the new recommendations will help reduce the risk of collecting blood and blood components from donors who may be infected with the Zika virus," Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said in a statement.
While there have been no reports to date of Zika virus entering the U.S. blood supply, the FDA said it considers the risk of blood transmission likely based on the current scientific understanding of how the virus and others like it are spread. There also have been recent reports of transfusion-associated infections outside of the United States. For instance, local officials in Brazil earlier this month said two people contracted Zika virus transmission through blood transfusions. Both cases were in Campinas, a city northwest of São Paulo; the first patient was a liver-transplant recipient, and the second a gunshot victim.
The FDA's guidance on Tuesday is in line with recommendations from a broad range of other groups in recent weeks.
The United Kingdom's National Health Service recently put in place a 28-day "self-deferral" period for prospective donors who have returned from any of the countries and territories affected by the virus. The American Red Cross has made the same appeal to travelers, saying the temporary policy was necessary despite the "extremely low" risk of Zika being transmitted through a blood transfusion in the United States.
The professional standards group AABB, formerly known as the American Association of Blood Banks, recently published a lengthy set of guidelines in response to the ongoing Zika outbreak. It said the 28-day, self-deferral policy "should be an effective measure to reduce the risk posed by Zika virus transfusion transmission," as well as the transmission of other tropical diseases, such as dengue and chikungunya.