As many as one in four people living in Puerto Rico could become infected with the Zika virus this year, CDC scientists warned.
The alert was prompted by samples of more than 12,700 blood tests taken on the island between April 3 and June 11, according to the New York Times. By the last week of testing, 1.1 percent of all blood donors in the U.S. territory had active Zika infections.
"There are a lot more Zika-positive people than we would anticipate this early," Phillip Williamson, an author of the CDC report, told the Times.
By the end of 2016 about 875,000 -- or a quarter of the island's population -- could be infected. That's dire news for Puerto Rico, and even worse news for pregnant women on the island.
The Zika virus, which spreads via mosquito bites, has been tied to the birth defect microcephaly and other fetal brain defects. The World Health Organization declared the Zika virus an international public health emergency in February, the same month officials identified the first U.S. infection, USA Today reported.
As of June 15 there were 756 confirmed cases of the Zika virus in the U.S., almost all of them categorized as "travel associated" -- meaning the victims were infected outside the country, the CDC said.
The CDC's director, Dr. Thomas Frieden, told Reuters on June 17 that the situation could become dire for pregnant women, the Times reports.
"It’s possible that thousands of pregnant women in Puerto Rico could be infected," Frieden said. Those infections could mean “dozens or hundreds of infants being born with microcephaly in the coming year.”
Zika-contaminated blood donations are removed from the blood supply in Puerto Rico thanks to an experimental test, but most blood banks in the continental U.S. have not begun using the screening procedure.