Researchers in U.S. have not established how it comes to infect humans
It hasn't infected just swimmers, which rules out direct link to algae itself
Instead humans could've been carrying virus but was not known to doctors
Research suggests it alters genes in brain including memory and emotion
Scientists found 44 per cent of patients tested had virus in their throats
By BEN SPENCER, SCIENCE REPORTER FOR THE DAILY MAIL
PUBLISHED: 16:05 GMT, 9 November 2014 | UPDATED: 11:57 GMT, 10 November 2014
Nearly half of us could be infected with a virus which makes us more stupid, scientists have found.
The startling discovery suggests that millions may be carrying a long-lasting infection which dulls the brain.
Scientists found the virus living in the throats of 44 per cent of patients tested in a small US study.
A viral infection that could make more than half of us stupid has been discovered by scientists in America
Those who were carrying the infection performed worse in intelligence tests, even when education and age were taken into account.
The virus - called chlorovirus ATCV-1 - was previously only known to appear in green algae in freshwater lakes.
The researchers, from Johns Hopkins University in Baltimore and the University of Nebraska, have not established how the virus comes to infect humans.
Instead it could be that humans have long carried the virus, but it had not previously been looked for by doctors.
Study author Professor Robert Yolken, of Johns Hopkins medical school, said the millions of viruses living in the human body are being investigated by experts for the first time.
‘We’re really just starting to find out what some of these agents that we’re carrying around might actually do,’ he told the Healthline website.
‘It’s the beginning, I think, of another way of looking at infectious agents — not agents that come in and do a lot of damage and then leave, like Ebola virus or influenza virus.
‘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.’
The research, published in the Proceedings of the National Academy of Sciences, suggests that the ATCV-1 virus alters the genes in the brain.
The team found the virus in throat swabs from 40 out of 92 volunteers, and discovered those with the virus performed measurably worse in cognitive testing.
They then confirmed their findings in tests on mice. Giving the virus to mice resulted in a decrease in recognition memory and other brain functions, they found.
Tests showed the virus had broken through the barrier between blood and tissue, altering the activity of genes in the brains of the mice.
The genes affected including those producing dopamine - a vital hormone which influences memory, spatial awareness, emotion and pleasure.
But the virus does not seem to have infected just swimmers or watersports fans, ruling out a link to algae itself
The virus - called chlorovirus ATCV-1 - was previously only known to appear in green algae in freshwater lakes
Professor James Van Etten, a biologist from the University of Nebraska who first identified the virus in algae 30 years ago, said: ‘There’s more and more studies showing that microorganisms in your body have a bigger influence than anything anyone would have predicted, and this could be something along those lines.’
Professor Yolken added: ‘The thing that’s different about what we found is that chlorovirus ATCV-1 is something that we wouldn’t have suspected would actually have any effect on humans or animals.
‘It points us in a direction of looking to see if we can improve people’s cognition, their behaviour, by changing the composition of their microbiome [the balance of bacteria and viruses in the body].’