WASHINGTON — Blood banks in the United States and Canada have begun turning away prospective donors who have visited Latin America in the past month to avoid contaminating the blood supply with the Zika virus, according to officials with the group that represents nearly all of the blood donation centers in the United States.

The AABB, formerly known as the American Association of Blood Banks, said it developed these guidelines with input from the Food and Drug Administration, as well as the American Red Cross, one of its members.

The FDA has said it is still developing its plans to ensure that the Zika virus does not infect the blood supply. Canada has just announced a one-month deferral on donations by people who have traveled to the Zika-affected countries.

“The FDA is still considering what to do about the Zika virus, and considering whether they want to make any binding recommendations,’’ said Dr. Steven Kleinman, AABB’s senior medical adviser. In the interim, AABB has issued recommendations to its members that call for blood banks to reject those donors.

The Red Cross, which handles about 40 percent of the US blood supply each year, said it would ask anyone who has traveled to Mexico, the Caribbean, or Central or South America within 28 days to voluntarily delay donations. Donors who have traveled to Zika-affected areas and show symptoms of the virus after they have donated are urged to notify the Red Cross as soon as they feel ill.

There are tests to detect the Zika virus, but they are complex and are now done only by the Centers for Disease Control and Prevention and a few state labs. Until they can be manufactured for use in blood banks, AABB also recommends that people who have traveled to Latin America or the tropics wait 28 days before donating blood.

Blood banks are being urged by AABB to require donors to monitor their health after they give blood, and report in if they have two of five symptoms: fever, muscle and joint pain, headache, eye pain, and rash.

The Zika virus is generally transmitted by the Aedes aegypti mosquito, which is prevalent in South America, Central America, and the Caribbean, but also found in parts of the southern United States.

Many people who contract the Zika virus develop only a mild infection, often with flu-like symptoms and a skin rash. Some don’t even know they have it. But scientists suspect that Zika has caused thousands of babies to be born with microcephaly, a birth defect characterized by abnormally small heads and underdeveloped brains. In Brazil, more than 4,100 babies were reported to have been born with microcephaly — significantly more than is normally seen.

Dr. Amesh Adalja, infectious disease physician at the University of Pittsburgh Medical Center’s Center for Health Security, said that, for blood banks, “self-deferral is a reasonable action to take at this time.’’

“We do need to develop a test quickly to screen donors, and it’s important to emphasize to the vast number of people that the Zika virus isn’t going to be bad,’’ he said.

Blood bank donor deferral has been used to stop the spread of infectious diseases through blood before. In some European countries, for example, travelers who have visited the United States during mosquito season must wait four weeks before donating, to ensure that they do not have West Nile disease.

The American Red Cross requires prospective donors to wait 12 months after traveling to a country where malaria is endemic before donating.

Sheila Kaplan can be reached at sheila.kaplan@stat news.com. Follow Stat on Twitter @statnews.