FDA says blood banks in 11 states, including California, must test for Zika by September

The federal government is taking action to prevent the Zika virus from entering the nation's blood supply.

The U.S. Food and Drug Administration announced Friday that blood banks nationwide should begin screening all donated blood units for the Zika virus within three months.

"We're recommending testing of donated blood throughout the United States and its territories. We're taking this step to further enhance the safety of the blood supply," said Dr. Peter Marks,  a U.S. Food and Drug Administration spokesman.

California is one of eleven states facing an earlier deadline to implement testing by the end of September.

Those states are Alabama, Arizona, California, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, New York, South Carolina and Texas.

Most of those states are close to Florida or Mexico where the Zika virus has been spread by mosquitoes.

Some states on the list have had a large number of Zika cases related to travel or sexual transmission. California has 170 such Zika cases.

Doctors say the concern is that blood donors might be carrying the Zika virus without knowing it.

"About 80% of people who are infected with Zika will never develop any symptoms and that's one reason why it's a risk to a unit of blood," said Dr. Suchitra Pandey, the Chief Medical Officer at the Blood Centers of the Pacific, which has donation centers throughout the Bay Area.

Dr. Pandey says that since February, they have been asking donors about whether they have traveled to Zika-risk zones or had sexual contact with someone who has traveled in those areas.

Dr. Pandey says the blood bank started a pilot Zika-testing program in July which it will now expand.

"Donors are tested for HIV, hepatitis C, West Nile virus, a number of other diseases, and so Zika would be added to that and we would get all of the results within 48 hours," said Dr. Pandey.

The Zika screening test is still new but doctors say it has already been used in Florida and Puerto Rico.

'It has not yet been FDA licensed, so it is still in the investigational phase. It is a nucleic acid test which means we are looking specifically for the virus's RNA in the bloodstream," Dr. Pandey said, adding that there are two manufacturers which make the Zika screening test and all samples are processed through a lab in Arizona.

The cost to blood banks and medical centers is still unknown.