Red Cross asks blood donors to hold off if they've been to Zika-stricken countries

Would-be blood donors who've recently traveled to Latin America or the Caribbean are being asked by the American Red Cross to hold off for four weeks before they donate .

On Wednesday, Red Cross officials began requesting potential donors to "self-defer" their donation for 28 days after returning from Mexico, the Caribbean, Central or South America. The idea is to prevent the spread of the Zika virus , which is carried by mosquitoes in those regions and other parts of the world.

While the virus itself presents mild symptoms such as fever, rash, joint pain or red eyes, some researchers believe that pregnant women exposed to the virus are put at risk of having babies with severe birth defects. Brazil, for example, has seen a spike in babies born with microcephaly , an abnormally small head, that has coincided with the spread of Zika there.

In a statement Wednesday , Red Cross officials noted that the risk of contracting Zika by blood transfusion in the continental United States is very low; at this point, there's yet been no widespread transmission here by mosquitoes, as there has been in other parts of the world.

The Red Cross is asking recent blood donors to watch out for Zika symptons within 14 days of their donation, and to notify them if they become ill so that the blood can be quarantined.

The statement reads: "as part of our current health screening process, we only collect blood from donors who are healthy and feeling well at the time of donation." But that a callback number is provided for those who might develop any illness symptoms afterward.