It appears this is the case for the Zika Virus. New research suggests that the harmful virus, which causes brain damage in developing babies, could be used to treat glioblastoma, a deadly form of brain cancer.

In a paper published in the Journal of Experimental Medicine, researchers found that Zika injections reduced the size of cancerous tumors in mice, leaving surrounding brain cells unaffected.

Zika attacks stem cells, which are abundant in babies’ brains as they develop in the womb, but not nearly as prevalent in adult brains. Glioblastoma originates from stem cells, however, which divide and grow in the brain as the cancer spreads. By specifically attacking these stem cells, the virus could offer a targeted line of attack.

“It looks like there’s a silver lining to Zika,” Michael Diamond, one of the study’s authors, told the BBC. “This virus that targets cells that are very important for brain growth in babies, we could use that now to target growing tumors.”

Mice are not humans, of course. But the results are promising enough that Diamond said he hopes to start trials on humans in less than two years.