Discovery of the algae virus was an offshoot as scientists were looking at microbes that live in the human throat.
Virologist Dr. Robert Yolken told The Independent,"this is a striking example showing that the 'innocuous' microorganisms we carry can affect behavior and cognition."
Nearly half the patients in the study tested positive for the virus. Doctors say that group didn’t do as well in tests measuring speed and accuracy in visual processing. They also had shorter attention spans.
Researchers point out the human body is home to trillions of mostly harmless or beneficial bacteria, viruses and fungi.
However, they contend this work proves some can leave a person physically healthy, but cause them to struggle mentally.
The results of the study have been published at the Proceedings of the National Academy of Sciences.