The Centers for Disease Control and Prevention issued a special travel advisory Tuesday for pregnant women — and those trying to get pregnant.
They should "consider postponing nonessential travel" to 11 countries, the agency says. These countries include Brunei, Cambodia, Indonesia, Laos, Malaysia, the Maldives, Myanmar, Philippines, Thailand, East Timor and Vietnam.
For Singapore, pregnant women "should not travel" there, the CDC says.
The agency has a stronger warning for Singapore compared to the rest of the region because Singapore is currently experiencing a large Zika outbreak. About 400 people have been diagnosed with virus since the end of the August.
Zika was first detected in Southeast back in the 1960's. And scientists think the virus has been circulating throughout the region since then.
"Several countries have reported occasional cases or small outbreaks of Zika," says the CDC's Dr. Denise Jamieson.
But then in the past month, health officials have started to detect more Zika cases around the region. Besides the outbreak in Singapore, cases have cropped up Thailand, the Philippines and Indonesia. Thailand is currently investigating cases of microcephaly to see if they're linked to Zika infection, the World Health Organization said Thursday.
"Although we believe the level of risk for Zika virus infection in Southeast Asia is likely lower than in Latin America — where the virus is spreading widely — we still feel there is some risk to pregnant women in Southeast Asia," Jamieson says.
The strain of Zika circulating in Latin America and the Caribbean is known to cause severe birth defects, including babies born with very small heads and brain damage.
Although the strain in Southeast Asia is slightly different than the one in Latin America, many scientists think the Asian strain will likely be just as dangerous to developing fetuses.
If pregnant women must travel to Southeast Asia, they should discuss the trip with their doctors. And while there, they should take strict precautions to prevent getting bitten by mosquitoes, the CDC says.
When they return from any region with Zika, pregnant women should get tested for the virus, whether they have symptoms or not.
Both men and women should wait six months after returning from Zika regions before trying to get pregnant, the World Health Organization says. They should also practice safe sex to prevent spreading the virus through sexual transmission.
"Sex includes vaginal, anal, and oral sex," the CDC says.