(Reuters) - The American Red Cross appealed on Tuesday to prospective donors who have visited Zika outbreak zones to wait at least 28 days before giving blood, but said risks of transmitting the virus through blood donations remained "extremely" low in the continental United States.
The "self-deferral" for blood donors should apply to those who have visited Mexico, the Caribbean, or Central or South America during the past four weeks, the Red Cross said in a statement.
The Washington-based nonprofit disaster relief agency also asked that donors who give blood and subsequently develop Zika-like symptoms within 14 days of that donation to notify the Red Cross so the product can be quarantined.
Cases of the Zika virus, a mosquito-born illness linked to a dangerous birth defect called microcephaly - marked by small head size - and to a serious autoimmune disorder called Guillian-Barre syndrome that can cause paralysis, has been reported in more than 30 countries and territories.
The Red Cross statement came as the first known case of Zika virus transmission in the United States was reported in Texas on Tuesday by local health officials, who said it likely was contracted through sex and not a mosquito bite. The World Health Organization on Monday declared an international public health emergency over the virus.
Zika had been thought to be spread by the bite of mosquitoes of the Aedes genus, so sexual contact as a mode of transmission would be a potentially alarming development.
(Reporting by Sara Catania in Los Angeles. Writing and additional reporting by Steve Gorman in Los Angeles; Editing by Richard Chang and Andrew Hay)