INDIANAPOLIS (AP): Officials with the Indiana Blood Center say they’ve had to defer up to 30 percent of donors at some post-spring break blood drives because they traveled to areas where the Zika virus is being transmitted.

The Indianapolis Star reports that the center fell about 400 units short of its monthly goal of 10,000 units in April.

Advice from the Food and Drug Administration prompted the center to begin screening donors for Zika-area travel in March. The federal government recommends that those who travel to areas where the virus is active wait a month after returning to donate blood.

Center officials have been asking donors who are planning a trip to the affected areas to donate before they go.

They’re also asking donors who haven’t traveled to help restock the center’s dwindling supplies.