A new study shows the Zika virus stays in the saliva, sex organs and nervous systems of monkeys even after the virus is gone from the blood. The report in Nature Medicine suggests certain organs may harbor the virus after the body's immune system has fought it off.

The report says "Early invasion of Zika virus into the nervous system of healthy animals and the extent and duration of shedding in saliva and semen underscore possible concern for additional neurologic complications." Although the research focuses on monkeys, it sheds some light on how the virus may act in humans.

Zika can cause birth defects in babies born to infected mothers.
Researchers worldwide are working on a vaccine.