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Researchers have identified a virus that can cause cognition problems but not show any symptoms even as they reside in human throats for many years.

According to IB Times, the virus ATCV-1 infects freshwater algae but can also infect mice and humans. As it is not associated with swimming or water sports, researchers are yet to determine how humans are infected. The virus's effects have however been understood; experiments have shown that it can reduce cognition and spatial recognition abilities by affecting the brain.

"This is a striking example showing that the 'innocuous' microorganisms we carry can affect behavior and cognition," says lead investigator Robert Yolken, a virologist and pediatric infectious disease specialist at Johns Hopkins, in a press release.

"Many physiological differences between person A and person B are encoded in the set of genes each inherits from parents, yet some of these differences are fueled by the various microorganisms we harbor and the way they interact with our genes."

The finding of the virus in throats was accidental. After discovering the presence of ATCV-1 DNA in the throats researchers conducted a small study involving 92 adults. They found that 40 adults had the virus in their throats, a 44 percent likelihood of presence.

Researchers then administered tests to measure brain performance and found that participants infected with ATCV-1 scored 7-9 points behind those not infected by the virus.

They then infected mice with virus and tested for cognitive performance through maze tests, only to find that infected mice were confused in the maze. Analysis of mice brain showed the virus altering genes and affecting the hippocampus region.

The similarity of our findings in mice and humans underscores the common mechanisms that many microbes use to affect cognitive function in both animals and people," says co-investigator Mikhail Pletnikov, director of the Behavioral Neurobiology and Neuroimmunology Laboratory at Johns Hopkins.

The study's findings have been published in the Proceedings of the National Academy of Sciences (PNAS).