The Zika virus has led pregnant women to avoid certain areas fearing for their infant’s health. However, the harmful virus could be the answer to brain cancer, according to a new study.

The virus could lead to an effective treatment for glioblastoma, a fatal type of brain cancer, researchers from Washington University School of Medicine in St. Louis and the University of California San Diego School of Medicine said Tuesday.

Researchers found the Zika virus can be used to target and kill brain cancer stem cells, which are the ones most resistant to standard treatments. The findings are published in the Journal of Experimental Medicine.

Glioblastoma is the most common type of brain cancer, with about 12,000 people in the U.S. diagnosed each year. Brain cancer came into the spotlight this summer when Sen. John McCain (R-Ariz.) announced in his diagnosis. Glioblastoma can often cause death within a year of diagnosis, but researchers believe the new discovery could improve a person’s chance against the cancer.

Standard treatment for glioblastoma includes surgery, followed by chemotherapy and radiation, however most tumors return within six months. This is due to brain cancer stem cells that survive the treatment and continue to divide, creating new tumor cells that replace the ones previously killed. The brain cancer stem cells reminded postdoctoral researcher Zhe Zhu, PhD, of neuroprogenitor cells.

“Zika targets fetal neuroprogenitor stem cells. Cancer stem cells share similarities with these cells,” the study’s co-senior author, Dr. Michael S. Diamond, told International Business Times.  “Zhe Zhu, a post-doctoral fellow, had the idea to see whether Zika could also target tumor stem cells.”

Researchers tested whether the Zika virus could kill the stem cells in glioblastomas removed from patients when diagnosed. The virus infected and killed the cancer stem cells, while it avoided the other tumor cells. Researchers believe the virus and chemotherapy-radiation treatments have complementary effects, since the Zika virus kills the stem cells and the latter treatment eradicates the bulk of the tumor cells.

“We were surprised at how well it did and how selective it was for certain tumor cells,” said Diamond.

To see if the Zika virus could help treat cancer in a living animal, researchers injected either the virus or a placebo, in this case salt water, into the brains tumors of mice. They found tumors were significantly smaller in the mice treated with Zika two weeks after the injection, while the tumors in mice injected with salt water survived for much longer.

Researchers say a treatment for humans using Zika means the virus will have to be injected into the brain, most likely during surgery to remove the primary tumor. If the virus is injected through the body, the patient’s immune system will fight away the virus before it reaches the brain, meaning that technique wouldn’t help eradicate the cancer.

Still, the idea of injecting the Zika virus into someone’s brain is scary. The Zika virus has been linked to the condition known as microcephaly, which affects infants. The virus has led to severe birth defects among infants in multiple countries.

However, researchers assure Zika is safer for use in adults because it goes after neuroprogenitor cells, which are rare in the adult brain, whereas fetal brains are packed with those cells. Researchers have also conducted other studies of the virus using brain tissue from people with epilepsy, which show the virus did not affect nonmalignant cells.

“We are planning to use a genetically modified Zika virus that will selectively target the tumor cells and not the normal brain cells,” Diamond told IBTimes. “By modifying the virus genetically, we will make hit more sensitive to the body’s natural immune defense system, however, cancer stem cells lack this defense. Thus, the virus can replicate and kill the tumor stem cells but not the healthy neurons.”

Diamond added there is still more work to be done before clinicians start using a treatment with Zika.

“If all goes well, we estimate we are ~18 months away from initiating human trials,” said Diamond. “This presumes we do not encounter technical or regulatory problems along the way.”