Scientists have found a new virus called Chlorovirus ATCV-1 that can affect cognitive function in humans and make them more stupid.

Scientists at the University of Nebraska and John Hopkins Medical School reveal that the ATCV-1 virus infects the green algae found in freshwater ponds and lakes. Previously, scientists believed that the virus was not harmful to humans; however, latest study reveals that the virus can affect cognitive functioning in human brain, which can shorten attention span and also cause reduced spatial awareness.

The researchers were conducting a separate study but found the DNA of ATCV-1 virus in human throat. The scientists conducted a test of 92 healthy individuals and found the virus in 40 people. Individuals who were infected with the virus performed 10 percent slower in visual processing tests.

The study found no link between reduced brain function and factors such as variances in sex, income, education level, race and smoking cigarette.

In a separate experiment, the scientists also injected the virus in the digestive tracts of lab mice. The researchers found that when these mice were put in a maze, they took 10 percent more time finding their way out when compared to normal mice.

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.

The scientists suggest that not only swimmers or people who have come in direct contact may have got infected. They suggest that many people may have been infected with the virus but are unaware. The scientists suggest that at this stage it is unclear how the virus is transmitted to humans and if it is contagious.

Professor Robert Yolken at Johns Hopkins Medical School, who is also the study author, reveals that millions of viruses live in human body and many of them have never been examined. As the virus does not cause extreme damage it may have never been investigated before, but now scientists are examining many viruses in the human body for the first time.

"This is kind of the other end of the spectrum. These are agents that we carry around for a long time and that may have subtle effects on our cognition and behaviour," says Professor Yolken.

The study has been published in the journal PNAS.