Blood banks in the U.S. now test potential donors for such conditions as West Nile Virus, HIV and hepatitis. But there is no approved testing for the Zika virus, which has been linked to birth defects.
Dr. Johnathan Hughes is a medical director with Blood Source, which supplies blood to the Sacramento area and Northern California.
He says most people infected with the Zika virus show no symptoms, so people who have recently traveled out of the country are not acceptable donors.
"We'll be deferring donors for a temporary period of time to not donate for 28 days after traveling to Mexico, all destinations in the Caribbean, Central, South America," says Hughes.