The virus, Chlorovirus ATCV-1, was previously found only in green algae - simple plants that live mostly in water - but researchers have now detected it in humans, where it seems to alter genes governing cognitive function.
Researchers at the University of Nebraska and John Hopkins Medical School were conducting a separate study but found the DNA of ATCV-1 virus in human throat, Tech Times reported.
They conducted a test of 92 healthy individuals and found the virus in 40 people. Individuals who were infected with the virus performed 10 per cent slower in visual processing tests.
Scientists also injected the virus in the digestive tracts of lab mice. They found that when these mice were put in a maze, they took 10 per cent more time finding their way out when compared to normal mice.
Researchers said the impact similarity of the virus in humans and mice determines that ATCV-1 virus impairs the brain function to a certain level and makes people more stupid.
Professor Robert Yolken at Johns Hopkins Medical School, who is also the study author, noted that millions of viruses live in human body and many of them have never been examined.