U.S. health officials are warning both men and women about attempting to become pregnant if they’ve had a Zika virus infection as fears over the sudden outbreak grow.

Officials say that men should wait six months and women should wait two months after a Zika virus infection before attempting to conceive, according to a Reuters report.

The Zika virus is believed to be behind thousands of cases of birth defects in Brazil, and the virus is quickly spreading north toward the United States. The Centers for Disease Control and Prevention issued guidance recently on preventing infections in women who are already pregnant.

It’s been just a year since the Zika virus, which is spread by mosquitoes, was first reported down in Brazil, and it has quickly spread throughout South America and into the Caribbean and Central America, with cases beginning to creep into the U.S.

The CDC is advising men who have been to areas with Zika transmission to use condoms during each sexual encounter, and to perhaps abstain from sex during a pregnancy.

Officials are still trying to get in front of the issue, as they don’t yet fully understand the virus and its potential effects.

Concerns are particularly strong in Puerto Rico, where Zika is infecting hundreds of pregannt women, and where contraception use isn’t strong to begin with.

The CDC has the following advice for people looking to avoid a Zika infection:

“There is no vaccine or medicine for Zika. Travelers can protect themselves by preventing mosquito bites:
•Cover exposed skin by wearing long-sleeved shirts and long pants.
•Use EPA-registered insect repellents containing DEET, picaridin, oil of lemon eucalyptus (OLE, also called para-menthane-diol [PMD]), or IR3535. Always use as directed. ◦Pregnant and breastfeeding women can use all EPA-registered insect repellents, including DEET, according to the product label. Most repellents, including DEET, can be used on children older than 2 months. (OLE should not be used on children younger than 3 years.)
•Use permethrin-treated clothing and gear (such as boots, pants, socks, and tents). You can buy pre-treated clothing and gear or treat them yourself.
•Stay in places with air conditioning and window and door screens to keep mosquitoes outside.
•Sleep under a mosquito bed net if air conditioned or screened rooms are not available or if sleeping outdoors.
•Mosquito netting can be used to cover babies younger than 2 months old in carriers, strollers, or cribs to protect them from mosquito bites.”