U.S. health officials on Thursday recommended that pregnant women postpone nonessential travel to 11 Southeast Asian countries because of the risk of Zika virus infection, which has been shown to cause severe birth defects.

The latest countries singled out by the U.S. Centers for Disease Control and Prevention are Brunei, Myanmar, Cambodia, Indonesia, Laos, Malaysia, Maldives, Philippines, Thailand, Timor-Leste (East Timor), and Vietnam.

The CDC said "travel notices," like those issued for Zika-struck countries like Brazil and Singapore, have not been issued for these destinations, but such warnings would be considered if the number of cases rises to the level of an outbreak.