FDA expands Zika screening to all blood centers in US

men can spread the virus for several months through sex, and women can transmit it for several weeks.

Adding to the challenge is that 4 out of 5 people infected never develop symptoms, such as fever, joint pain and rash.

The Centers for Disease Control and Prevention on Friday reported the first U.S. case of a man spreading Zika through sex even though he never had any symptoms. The Maryland man had traveled to the Dominican Republic, one of the many countries in the Caribbean and Latin America hit with a Zika outbreak.

There have been nearly 2,500 cases of Zika in the U.S. linked to travel to outbreak areas. Since February, blood banks have turned away people who had recently visited those regions, under a previous FDA directive.

While the virus causes only a mild illness in most people, infection during pregnancy can lead to severe brain-related birth defects.

Blood testing began last month in parts of Florida after the first cases of homegrown Zika occurred in Miami. So far, there have been about 40 cases of Zika caused by mosquito bites in Florida. Health officials, however, don’t expect widespread outbreaks to occur in the U.S.

The tropical mosquito that spreads Zika and other viruses is found along the southern U.S. Friday’s directive lists 11 states that will need to begin screening blood in the next month because of their location or because of the influx of travelers from Zika outbreak countries.

On the list: Alabama, Arizona, California, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, New York, South Carolina and Texas. All other U.S. states and territories will have three months to comply.