Roughly 1 percent of recent blood donors in Puerto Rico showed signs of active infection with the Zika virus, suggesting that a substantial portion of the island’s population will become infected, federal health officials reported on Friday.
From April 3 to June 11, testing of 12,700 donations at blood centers in Puerto Rico identified 68 infected donors, according to the Centers for Disease Control and Prevention.
Over all, about 0.5 percent of donors had active Zika infections, but the prevalence rose to 1.1 percent in the week ending June 11. The virus, carried by the yellow fever mosquito, has been linked to birth defects in infants and neurological problems in adults.
“There are a lot more Zika-positive people than we would anticipate this early” in the outbreak, said Phillip Williamson, an author of the C.D.C. report and the vice president of operations at Creative Testing Solutions, a blood-donor testing laboratory.
Based on prior experience, Dr. Williamson said he would not have expected so many Zika-infected donors until late June or early July.
The C.D.C. has estimated that as many as a quarter of the island’s 3.5 million people may become infected with the Zika virus this year.
“It’s possible that thousands of pregnant women in Puerto Rico could be infected,” Dr. Thomas R. Frieden, the agency’s director, told Reuters on Friday, leading to “dozens or hundreds of infants being born with microcephaly in the coming year.”
Zika-contaminated donations are removed from the blood supply. In the continental United States, where local transmission of the virus has yet to be reported, most blood banks are not yet using the experimental screening test used in Puerto Rico, which was made by Roche Diagnostics.