Zika virus could potentially spread through contaminated blood donations, and while some samples have tested positive for Zika, the samples tested in 12 states so far show Zika is an "exceedingly rare" occurrence in donated blood, according to The New York Times.
At the end of August, the FDA issued guidance mandating all blood samples be screened for Zika by no later than Nov. 18. Some states — Florida, Alabama, Arizona, California, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, New York, South Carolina and Texas — had to do so sooner.
So far, in those 12 states, just 40 samples out of about 800,000 tested positive for Zika, according to the Times. The low number may be because blood banks have been encouraging people to skip donating if they had traveled to a location with active Zika transmission.
Blood banks can either screen the donations themselves or send them to a lab for testing. According to the Times, this process has increased the price hospitals pay for blood.