Federal health authorities said for the first time on Friday how long couples who have been exposed to the Zika virus should wait before trying to get pregnant.

The officials, at the Centers for Disease Control and Prevention, said that they had decided to recommend a waiting period based on the latest information about the science of the virus. The Zika virus has been linked to a surge of birth defects in Brazil, and to cases of Guillain-Barré syndrome, in which a person’s immune system attacks part of the nervous system, leading to some paralysis.

Women who have had symptoms of the virus or tested positive for it should wait at least eight weeks after their symptoms first appeared before trying to get pregnant, the agency said. Officials recommended that men who had symptoms should wait six months before having unprotected sex. The virus has been known to live longer in semen. Symptoms can include rashes and sore joints.