Researchers from Washington University School of Medicine discovered that Zika can persist in the eyes. They found genetic material from the virus in tears, which can explain why patients affected with Zika develop eye diseases.

As reported in the journal Cell Reports, the research team claim that their study on mice demonstrated that the eye can be a reservoir for the virus. Among the eye diseases that a patient can suffer is uveitis,  which can cause permanent vision loss.

They found that a third of babies who have been infected with Zika while still in the uterus suffer from optic nerve inflammation, retinal damage and even blindness after birth. On the other hand, adult patients with the virus suffer from uveitis and conjunctivitis, redness and itchiness of the eyes.

The study involved infecting adult mice with Zika. The team injected the virus under the animals’ skin. Seven days later, the  RNA or the genetic material from the virus was found in their eyes.

The researchers cannot explain how the virus traveled to the eye.  Still, this shows that people can be infected with Zika when they come in contact with tears from the infected patients.

“Even though we didn’t find live virus in mouse tears, that doesn’t mean that it couldn’t be infectious in humans,” points out lead author Jonathan  Miner. “There could be a window of time when tears are highly infectious and people are coming in contact with it and able to spread it.”

The researchers plan to conduct studies on people to find out whether infectious virus persists in the cornea or other compartments of the eye, which is considered as an immune privileged site because the immune system is not as active there as it is in other body parts.

However, if they find that human tears are not infectious, they could still use this method to diagnose Zika infection without the need of drawing blood.  Moreover, anti-Zika drugs could also be tested on the eyes without conducting invasive procedures.