Now, scientists say they've gained new insight into how the virus infects the fetus, and a potential means of preventing infection.
Zika can cause serious birth defects if a woman becomes infected while pregnant. Thousands of babies have been born in Brazil with abnormally small heads and brains, a condition called microcephaly.
"Very few viruses reach the fetus during pregnancy and cause birth defects," noted study lead researcher Lenore Pereira, a professor of cell and tissue biology at the University of California, San Francisco.
Gaining a better understanding of how Zika does this "may be the most essential question for thinking about ways to protect the fetus when the mother gets infected," she said in a university news release.
Based on work in the laboratory, Pereira's team discovered that Zika infects numerous types of cells in the placenta and amniotic sac, the fluid-filled sac that surrounds and protects the fetus in the womb. The virus also takes two distinct routes to reach a developing fetus.
There is a placental route, established in the first trimester of pregnancy, or a route across the amniotic sac that only becomes available in the second trimester, the research team reported.
In their tests, the researchers also found that an older antibiotic called duramycin effectively blocked the virus from replicating in the type of cells that they believe help transmit Zika along both routes.
In prior lab work, duramycin has been found to help fight off dengue and West Nile viruses, which are flaviviruses -- the same group of viruses that comprises Zika.
"Duramycin efficiently blocks infection of numerous placental cell types and intact first-trimester human placental tissue by contemporary strains of Zika virus recently isolated from the current outbreak in Latin America," study co-author Eva Harris said in the news release. She is professor of infectious diseases and vaccinology at the University of California, Berkeley's School of Public Health.
Early science like this often fails to pan out in humans, so more research is necessary. However, Harris believes that "duramycin or similar drugs could effectively reduce or prevent transmission of Zika virus from mother to fetus across both potential routes and prevent associated birth defects."
The findings were published July 18 in the journal Cell Host & Microbe.
The U.S. Centers for Disease Control and Prevention provides more information on mosquito-borne diseases.
This Q&A will tell you what you need to know about Zika.
To see the CDC list of sites where Zika virus is active and may pose a threat to pregnant women, click here.
Copyright © 2016 HealthDay. All rights reserved.