Over 1% of Blood Donors in Puerto Rico Infected with Zika

By Kelly Young

Edited by Susan Sadoughi, MD, and André Sofair, MD, MPH

Puerto Rico has seen a steady increase in Zika virus infections in recent weeks.

Using a new nucleic-acid test to screen blood donors for the Zika virus, researchers report in MMWR that 68 of 13,000 potential donors (0.5%) tested positive for Zika. The highest rate (1.1%) was for the most recent week (June 5–11).

"We do believe, based on what has happened with other viruses that the blood donor population gives us our most real-time leading indicator of what is happening with infections in the population as a whole," CDC Director Thomas Frieden told reporters. "Even though it's not a random sample or a systematic sample, it's a large number of people being tested from all walks of life."

Based on the histories of other mosquito-borne illnesses, hundreds of fetuses may be at risk for Zika-related complications in that territory. With Chikungunya, roughly a quarter of the Puerto Rican population became infected within a year of virus introduction, and the Zika blood donor test results indicate a similar rate of infection early in the season. "Only time will tell for sure, but it's certainly very concerning because of the risk to pregnant women," Frieden said.