Zika's second avenue of transmission has less to with bugs than with the birds and the bees. Evidence suggests that a man can transmit the virus to his sex partners, although this is probably not common, and in most known cases the men experienced symptoms such as genital pain and bloody semen. We know that the virus persists in semen longer than in blood (a few months versus 7 to 10 days), but we don't know how long semen remains infectious. We also don't know whether a woman can transmit Zika to a sexual partner, or what types of sexual contact (e.g., anal or oral) could spread it [sources: CDC, McNeil et al., Steenhuysen].
It's also possible that Zika can spread through blood transfusions and that the virus lives on in saliva and urine, although its transmissibility via these fluids remains an open question [sources: CDC, McNeil et al., Rampton and Hirschler].
Although cases remain rare, mothers can transmit Zika to fetuses, typically at or near the time of birth. Infection might also occur during pregnancy, but the jury is still out on this [sources: CDC, pregnancy; CDC, transmission]. If true, then infection earlier in pregnancy is likely more dangerous [source: McNeil et al.]. Researchers have detected Zika RNA in breast milk but have yet to see transmission through that route, so the benefits of breastfeeding still outweigh the risks [source: CDC].
According to the CDC, EPA-registered insect repellents that contain DEET, picaridin and IR3535 are safe for use during pregnancy.
Given the sexual knowns and unknowns, the safest plan for people at risk of having, getting or giving Zika lies in abstinence or in using condoms the right way every time. Along similar lines, countries such as Brazil, Colombia, El Salvador and Honduras have called for women to put off having children for a few years [sources: CDC, McNeil et al., Wade]. Initially, Latin American Catholic bishops balked at the mention of contraceptives, but Pope Francis has since relaxed the church's stance in cases of likely Zika infection [sources: Goodstein, NPR]. The Pope still strongly denounces abortion, however, which means that pregnant women affected by these issues will face significant resistance from both the Catholic Church and, in many countries, the legal system if they decide to terminate their pregnancies.
Further complicating matters, Zika is hard to diagnose in adults, let alone fetuses. There's no widely available test, and procedures such as amniocentesis carry risks of injury to the baby and rendering false positives. In part, this is because we can only detect Zika in the first week — after that, we're detecting antibodies, which closely resemble the antibodies of Zika's cousins (and their vaccines) [sources: CDC, McNeil et al.].
Bottom line: If you got pregnant before/during recent travel to a country with Zika, see a doctor and get a blood test 2 to 12 weeks after returning. Have ultrasounds done, too, but prepare yourself for the fact that your doctor won't be able to spot microcephaly before the end of the second trimester. If you get pregnant after travel to a country with a Zika outbreak, your risk is much lower, but you should still have your newborn tested. Even if your child does not have microcephaly, other birth defects (e.g., vision and hearing) might still occur [sources: CDC, McNeil et al.].