Men who have been infected with the Zika virus should not attempt to father a child for at least six months after their illness, and women who have been infected should wait at least eight weeks before trying to conceive, the Centers for Disease Prevention and Control said Friday.

The new recommendations reflect the agency’s concern that transmission of the virus could occur at or around the time of conception and affect the health of the fetus, according to Dr. Denise Jamieson, a member of the CDC’s Zika response team.

Up until now, the CDC has focused its recommendations on preventing sexual transmission of Zika to women who are already pregnant.

The new advice to delay conception relates to men and women who have been diagnosed with Zika or who have had symptoms and are suspected of having been infected.

Jamieson said some couples living in places where Zika is spreading locally may decide to delay pregnancy. Currently three US territories are experiencing local spread: Puerto Rico, American Samoa, and the US Virgin Islands.

But when asked if the CDC was considering urging women in these locations to postpone getting pregnant, Jamieson side-stepped the question.

“I think decisions regarding when and how to have children are personal and complex,” she said, adding that CDC’s job is to give people information with which to make those decisions.

The guidance is based on limited data, the agency acknowledged, and may need to be updated as more becomes available.

The United States has recorded six cases of sexual transmission of the virus since the current outbreak in the Americas began, and other countries — Argentina, Austria, Italy, and France — have also seen such cases.

There have been reports in the scientific literature of infectious virus being found in semen at least two weeks after the onset of symptoms of Zika infection. And scientists in Britain reported finding traces of the virus in the semen of a man 62 days after he became ill.

The CDC also raised concerns Friday that access to contraception is inadequate in Puerto Rico, which is expected to be hit hard by the Zika virus.

The agency estimates that one in five people on the island will have been infected by the end of 2016. Already 258 locally acquired cases of Zika infection have been detected there, and at least 24 of those people are pregnant women.

As many as 138,000 women in Puerto Rico who don’t want to become pregnant aren’t using effective contraception, the agency estimated, adding cost and availability are barriers to increased use there.

A study suggested 65.5 percent of pregnancies in Puerto Rico are unplanned. And the island’s teen pregnancy rate is 67 percent higher than that of the US mainland. In Puerto Rico, 40 teens out of every 1,000 become pregnant, compared to 24 per 1,000 teens in the US.