A new study published in the scientific journal Cell Reports is shedding new light on the Zika virus's interaction with the eyes. Researchers at the Washington University School of Medicine in St. Louis performed this informative test.
The scientists injected the Zika virus into a group of mice and observed the effects the virus had on their eyes over time. They looked at mouse fetuses, newborns, and adults. What they found was that the eye definitely serves as a breeding ground for the virus. This leads many researchers to believe that the virus could spread not only through sex and mosquito bites, but also via bodily fluids like tears.
Researchers observed that the mice they infected with the Zika virus had a live sample of the disease in their eyes seven days after they injected the disease into them. However, the virus did not appear in the eyes of newborn mice eight days after being born by an infected mother.
When they looked into the tears produced by infected mice, researchers found that Zika's RNA was still present 28 days after infection. However, this RNA was not at all infectious. Although these tears seemed to be harmless in mice, researchers are not sure if tears produced by humans with Zika's RNA will be the same.
Since the Zika virus lives in the eyes, this explains why many people infected with Zika virus have severe eye symptoms. Some people with Zika have even developed pain behind the eyes, red eyes, and, in rare cases, blindness.
After this study, researchers of the Zika virus have confirmed that Zika can live in a person's blood, semen, urine, breast milk, saliva, along the genital tracts, and in the eyeballs. With this new information, medical authorities now believe that the elderly Utah man who picked up Zika on a trip abroad may have spread the disease to his son through tears. Although the father died this June, his son has since recovered from the illness.
The main reason why doctors often test the eyes for traces of different viruses is because the eyes have a higher susceptibility for carrying them. Since the eye has a lower immune response to protect its soft tissue, it is a perfect breeding ground for all kinds of infections.
This is the reason why the American doctor Ian Crozier, who traveled to West Africa to help people infected with Ebola in 2014, but who got infected with Ebola himself, still had the Ebola virus in his eyes for many months after he was officially "cured."
In the near future, researchers are hoping to get a clearer idea on how long the Zika virus lasts in the eyes. Researchers also hope that further tests will show just how dangerous this disease is when spread through contact with human tears. Many medical professionals have also expressed interest in looking into what impact Zika virus has on the cornea.