The mosquito-borne virus that causes Rift Valley fever may severely injure human fetuses if contracted by mothers during pregnancy, according to new research.

In a study published last month in the journal Science Advances, researchers used infected rats and human fetal tissue to discover how the virus targets the placenta. Results showed that the virus may be even more damaging to fetuses than the Zika virus, which set off a global crisis in 2015 and left thousands of babies in Central America and South America with severe birth defects.

“Zika caught everybody by surprise,” said Amy Hartman, an infectious disease specialist at the University of Pittsburgh, who led the research. “If doctors had known about Zika’s birth effects, they could have done a lot more to protect pregnant women and babies. With Rift Valley fever, we’re trying to get ahead of the curve.”

Rift Valley fever primarily occurs in livestock in sub-Saharan Africa, where outbreaks cause 90 to 100 percent of pregnant cows in a herd to miscarry or deliver stillborn calves, often a significant economic loss.