U.S. officials on Friday issued their strongest travel warning yet regarding Zika, urging pregnant women to "consider not going" to the 2016 Summer Olympic Games in Rio de Janeiro.

The Centers for Disease Control and Prevention called the outbreak of the virus in Brazil, which is suspected of being the cause of possibly thousands of babies being born with birth defects, "dynamic" and said that women who are pregnant should avoid any area with active Zika transmission. That includes a broad swath of Latin America as well as four destinations in the Pacific Islands. The full list of countries and territories included has been updated frequently in recent weeks and can be found here.

The CDC also warned that pregnant women who have a male partner who goes to the Olympics may be at risk of sexual transmission of Zika. "Either use condoms the right way, every time, or do not have sex during your pregnancy," the CDC advised. Pregnant women who "must go" to the Olympics should talk to a health-care provider first and strictly follow steps to prevent mosquito bites during the trip.

Athletes have expressed increasing concern about their own risk during the Games. In an interview this month with Sports Illustrated, U.S. women's national team goalie Hope Solo said, "If I had to make the choice today, I wouldn’t go." Marina Alabau of Spain, a gold medalist in windsurfing, told the Associated Press that she got Zika while training in Brazil in December but that would not stop her from competing in August.

The advisory also includes advice for women who are trying to become pregnant. The CDC said they should talk to their doctors about the risk of Zika infection.

Read more:

For more health news, you can sign up for our weekly newsletter here.